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1

Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials  

NASA Astrophysics Data System (ADS)

The objective of this work was to provide a comprehensive evaluation of natural fiber reinforced polymer (NFRP)'s ability to act as a structural material. As a chemical treatment, aligned kenaf fibers were treated with sodium hydroxide (alkalization) in different concentrations and durations and then manufactured into kenaf fiber / vinyl ester composite plates. Single fiber tensile properties and composite flexural properties, both in dry and saturated environments, were assessed. Based on ASTM standard testing, a comparison of flexural, tensile, compressive, and shear mechanical properties was also made between an untreated kenaf fiber reinforced composite, a chemically treated kenaf fiber reinforced composite, a glass fiber reinforced composite, and oriented strand board (OSB). The mechanical properties were evaluated for dry samples, samples immersed in water for 50 hours, and samples immersed in water until saturation (~2700 hours). Since NFRPs are more vulnerable to environmental effects than synthetic fiber composites, a series of weathering and environmental tests were conducted on the kenaf fiber composites. The environmental conditions studied include real-time outdoor weathering, elevated temperatures, immersion in different pH solutions, and UV exposure. In all of these tests, degradation was found to be more pronounced in the NFRPs than in the glass FRPs; however, in nearly every case the degradation was less than 50% of the flexural strength or stiffness. Using a method of overlapping and meshing discontinuous fiber ends, large mats of fiber bundles were manufactured into composite facesheets for structural insulated panels (SIPs). The polyisocyanurate foam cores proved to be poorly matched to the strength and stiffness of the NFRP facesheets, leading to premature core shear or delamination failures in both flexure and compressive testing. The NFRPs were found to match well with the theoretical stiffness prediction methods of classical lamination theory, finite element method, and Castigliano's method in unidirectional tension and compression, but are less accurate for the more bond-dependent flexural and shear properties. With the acknowledged NFRP matrix bonding issues, the over-prediction of these theoretical models indicates that the flexural stiffness of the kenaf composite may be increased by up to 40% if a better bond between the fiber and matrix can be obtained. The sustainability of NFRPs was examined from two perspectives: environmental and socioeconomic. While the kenaf fibers themselves possess excellent sustainability characteristics, costing less while possessing a lesser environmental impact than the glass fibers, the vinyl ester resin used in the composites is environmentally hazardous and inflated the cost and embodied energy of the composite SIPs. Consistent throughout all the designs was a correlation between the respective costs of the raw materials and the respective environmental impacts. The socioeconomic study looked at the sustainability of natural fiber reinforced composite materials as housing materials in developing countries. A literature study on the country of Bangladesh, where the fibers in this study were grown, showed that the jute and kenaf market would benefit from the introduction of a value-added product like natural fiber composites. The high rate of homeless and inadequately housed in Bangladesh, as well as in the US and throughout the rest of the world, could be somewhat alleviated if a new, affordable, and durable material were introduced. While this study found that natural fiber composites possess sufficient mechanical properties to be adopted as primary structural members, the two major remaining hurdles needing to be overcome before natural fiber composites can be adopted as housing materials are the cost and sustainability of the resin system and the moisture resistance/durability of the fibers. (Abstract shortened by UMI.)

Dittenber, David B.

2

Mechanical Properties of Composite Material Using Natural Rubber with Epoxy Resin  

Microsoft Academic Search

In this paper the mechanical properties of three types of composite materials using natural rubber vulcanized, unvulcanized and reinforced rubber have been investigated . The composite material using natural rubber and epoxy resin is manufactured by three methods, first method is mixing the natural rubber with epoxy resin by special mixer without any additional materials, the second method is to

Hani Aziz Ameen

3

Composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A. (Knoxville, TN); Woodward, Jonathan (Solihull, GB); Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN)

2012-02-07

4

Composite Materials  

NSDL National Science Digital Library

This is an activity (located on page 3 of PDF) about composites, materials made of 2 or more different components. Learners will be challenged to build the best mud bricks, one of the earliest examples of composites. From a supply of various building components, which the learners will examine for their different properties, they will build mud bricks, then dry them and put them through several tests. *Bricks must bake in the sun for 2-3 days prior to testing. Resource contains information about how this activity relates to carbon nanotubes and links to video, DragonflyTV Nano: Hockey Sticks.

Twin Cities Public Television, Inc.

2008-01-01

5

Use of natural particles for the removal of paint from aeronautical composite materials  

NASA Astrophysics Data System (ADS)

Paint removal by blasting and its effects on the surface morphology of aeronautical composite materials are investigated. An ideal combination of the parameters for mechanical paint removal by blasting such as particle type, size, velocity and angle of incidence yields a stripped aircraft skin substrate with minimal or no damage. Natural particles, specifically white corn flour, seem to be a good choice for paint removal by blasting. Since they are softer as well as smaller in size than other particles used for paint removal, they minimize the amount of damage to the surface of the composite. They are also cheaper and produce no harm to environment. The variation of the degree of surface roughness and the amount of broken fibers were correlated with some stripping parameters, such as particle impact angle and velocity. This defined an optimum environment for paint removal by blasting.

Guy, Thu-Ha; Lankarani, Hamid M.; Talia, Jorge E.

6

Composite Materials  

NASA Technical Reports Server (NTRS)

Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

1985-01-01

7

Natural frequencies of composite plates with random material properties using higher-order shear deformation theory  

Microsoft Academic Search

Composites are known to display a considerable amount of scatter in their material properties due to large number of parameters associated with the manufacturing and fabrication processes. In the present work, the material properties have been taken as random variables for accurate prediction of the system behavior. Higher order shear theory including rotatory inertia effects has been accounted for in

B. N. Singh; D. Yadav; N. G. R. Iyengar

2001-01-01

8

Composite Materials Handbook  

NSDL National Science Digital Library

From the US Army Research Laboratory, Materials Sciences Corporation, and University of Delaware Center for Composite Materials, the Composite Materials Handbook provides the "information and guidance necessary to design and fabricate end items from composite materials." Along with current information on the material properties of these composite materials, the handbook also includes data development and usage guidelines. The information has been divided into three areas: polymer, metal, and ceramic matrix composites. The Polymer Matrix Composites Handbook (three volumes including Guidelines for Characterization of Structural Materials; Material Properties; and Materials Usage, Design, and Analysis) and the Metal Matrix Composites Handbook (one volume, .pdf) are available here. The Ceramic Matrix Composites Handbook has yet to be completed. Users may also download Quick Composites Data in spreadsheet format.

9

Composite structural materials  

NASA Technical Reports Server (NTRS)

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R. G.; Wiberley, S. E.

1985-01-01

10

Composite structural materials  

SciTech Connect

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R.G.; Wiberley, S.E.

1985-08-01

11

Composite structural materials  

NASA Technical Reports Server (NTRS)

Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

12

Tough Composite Materials  

NASA Technical Reports Server (NTRS)

Papers and working group summaries are presented which address composite material behavior and performance improvement. Topic areas include composite fracture toughness and impact characterization, constituent properties and interrelationships, and matrix synthesis and characterization.

Vosteen, L. F. (compiler); Johnson, N. J. (compiler); Teichman, L. A. (compiler)

1984-01-01

13

Composite structural materials  

NASA Technical Reports Server (NTRS)

A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

14

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1984-01-01

15

Composite structural materials  

NASA Technical Reports Server (NTRS)

The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

Ansell, G. S.; Wiberley, S. E.

1978-01-01

16

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

17

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1988-06-20

18

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1984-01-01

19

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

1989-01-01

20

Composite structural materials  

NASA Technical Reports Server (NTRS)

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Loewy, R.; Wiberley, S. E.

1986-01-01

21

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2001-01-01

22

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2002-01-01

23

Mechanics of Composite Materials  

Microsoft Academic Search

The mechanical behavior of composites is traditionally evaluated on both microscopic and macroscopic scale to take into account inhomogeneity. Micromechanics attempts to quantify the interactions of fiber and matrix (reinforcement and resin) on a microscopic scale on par with the diameter of a single fiber. Macromechanics treats composites as homogeneous materials, with mechanical properties representative of the laminate as a

Robert M. Jones

1999-01-01

24

Composite structural materials  

NASA Technical Reports Server (NTRS)

Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1982-01-01

25

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

26

Resin composite restorative materials.  

PubMed

This paper surveys the most important developments in resin-based dental composites and focuses on the deficits (e.g. polymerization shrinkage) and strengths of the materials and their clinical implications. Moreover, differences between composite categories, such as hybrid, nanohybrid, microfilled, packable, ormocer-based, silorane-based, polyacid-modified composites (compomers) and flowable composites are highlighted, especially in view of their mechanical behaviour. In addition to the classical dimethacrylate-based composites, special attention is given to alternative monomers, such as siloranes, ormocers or high-molecular-weight dimethacrylate monomers (e.g. dimer acid-based dimethacrylates and tricyclodecane (TCD)-urethane), analysing their advantages, behaviour and abilities. Finally, the paper attempts to establish the needs and wishes of clinicians for further development of resin-based composites. PMID:21564116

Ilie, N; Hickel, R

2011-06-01

27

Nanostructured composite reinforced material  

DOEpatents

A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

Seals, Roland D. (Oak Ridge, TN); Ripley, Edward B. (Knoxville, TN); Ludtka, Gerard M. (Oak Ridge, TN)

2012-07-31

28

Modified Composite Materials Workshop  

NASA Technical Reports Server (NTRS)

The reduction or elimination of the hazard which results from accidental release of graphite fibers from composite materials was studied at a workshop. At the workshop, groups were organized to consider six topics: epoxy modifications, epoxy replacement, fiber modifications, fiber coatings and new fibers, hybrids, and fiber release testing. Because of the time required to develop a new material and acquire a design data base, most of the workers concluded that a modified composite material would require about four to five years of development and testing before it could be applied to aircraft structures. The hybrid working group considered that some hybrid composites which reduce the risk of accidental fiber release might be put into service over the near term. The fiber release testing working group recommended a coordinated effort to define a suitable laboratory test.

Dicus, D. L. (compiler)

1978-01-01

29

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1983-01-01

30

Orthopedic Composite Materials.  

National Technical Information Service (NTIS)

The program was designed as a pilot project to establish new techniques for making orthopedic prosthetic materials. The basic idea was to make metal supported ceramic composites, so that the metal provided strength (and an element of ductility) and the re...

B. J. Shaw

1972-01-01

31

Introduction to Advanced Composite Materials  

NSDL National Science Digital Library

This presentation provides an introduction to composite materials and curriculum guidelines. Topics include applications of composites, advantages and disadvantages, and advice for developing a curriculum on advanced composite materials. This document is available for download as a PDF.

Stuart, Joe

2012-10-15

32

Erosion of composite materials  

NASA Technical Reports Server (NTRS)

A model for describing the response of uncoated and coated fiber reinforced composites subjected to repeated impingements of liquid (rain) droplets is presented. The model is based on the concept that fatigue is the dominant factor in the erosion process. Algebraic expressions are provided which give the incubation period, the rate of mass loss past the incubation period, and the total mass loss of the material during rain impact. The influence of material properties on erosion damage and the protection offered by different coatings are discussed and the use of the model in the design in the design of structures and components is illustrated.

Springer, G. S.

1980-01-01

33

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

Baucom, Robert M.

1991-01-01

34

Liquid Helium Composite Regenerator Material.  

National Technical Information Service (NTIS)

A cryogenic composite material designed for application to gap regenerators in cyclic cryocoolers operating below 10 K is investigated. The material is a composite of helium self-loaded into a metallic extended surface structure whose dispersion form is s...

T. R. Knowles

1987-01-01

35

Multifunctional Autonomically Healing Composite Material.  

National Technical Information Service (NTIS)

A composite material, contains a polymer, a polymerizer, a corresponding catalyst for the polymerizer, and a plurality of capsules. The polymerizer is in the capsules. The composite material is self-healing.

J. S. Moore N. R. Sottos P. H. Geubelle S. R. Sriram S. R. White

2005-01-01

36

Natural Fiber Composites: A Review  

SciTech Connect

The need for renewable fiber reinforced composites has never been as prevalent as it currently is. Natural fibers offer both cost savings and a reduction in density when compared to glass fibers. Though the strength of natural fibers is not as great as glass, the specific properties are comparable. Currently natural fiber composites have two issues that need to be addressed: resin compatibility and water absorption. The following preliminary research has investigated the use of Kenaf, Hibiscus cannabinus, as a possible glass replacement in fiber reinforced composites.

Westman, Matthew P.; Fifield, Leonard S.; Simmons, Kevin L.; Laddha, Sachin; Kafentzis, Tyler A.

2010-03-07

37

Natural Fiber or Glass Reinforced Polypropylene Composites?  

NASA Astrophysics Data System (ADS)

Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

Lorenzi, W.; di Landro, L.; Casiraghi, A.; Pagano, M. R.

2008-08-01

38

Composite material and method for production of improved composite material  

NASA Technical Reports Server (NTRS)

A laminated composite material with improved interlaminar strength and damage tolerance having short rods distributed evenly throughout the composite material perpendicular to the laminae. Each rod is shorter than the thickness of the finished laminate, but several times as long as the thickness of each lamina. The laminate is made by inserting short rods in layers of prepreg material, and then stacking and curing prepreg material with rods inserted therethrough.

Farley, Gary L. (Inventor)

1996-01-01

39

Composite materials for thermal energy storage  

SciTech Connect

This patent describes a composite material for thermal energy storage comprising a solid state phase change material selected from the group cnsisting of pentaerythritol, pentaglycerine, neopentyl glycol, tetramethylol propane, monoaminopentaerythritol, diaminopentaerythritol, tris(hydroxymethyl)acetic acid, and mixtures thereof. The solid state phase cange material contacts materials selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof.

Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

1986-02-25

40

Composite structural materials. [aircraft structures  

NASA Technical Reports Server (NTRS)

The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1980-01-01

41

Vibrational damping of composite materials  

NASA Astrophysics Data System (ADS)

The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss factor and modulus could be tailored by changing the angle, were produced and investigated. The addition of particles between composite prepreg layers to increase damping was studied. Electroviscoelastic materials that drastically changed properties such as loss factor and modulus with an applied voltage were manufactured and tested.

Biggerstaff, Janet M.

42

Fracture of laminated composite materials  

Microsoft Academic Search

Cracks occurring in conventional laminates, or artificially bonded composites, and slip bands appearing in lamellar alloys, or naturally bonded composites, are studied. In this analysis, a mixed mode plane crack is modeled by continuous distributions of both climb and glide dislocations. The requirement that the boundary conditions prescribed on the surfaces of this crack must be satisfied results in dual

Omoike

1984-01-01

43

Invariant Properties of Composite Materials.  

National Technical Information Service (NTIS)

Invariant properties of the elastic coefficient matrices of laminated composite plates are presented. The use of these invariants in materials evaluation and design optimization is discussed. Simple formulas, based upon micromechanics results, are derived...

N. J. Pagano S. W. Tsai

1968-01-01

44

Ultrasonic stress wave characterization of composite materials  

NASA Technical Reports Server (NTRS)

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.

1986-01-01

45

Left Handed Materials Using Magnetic Composites.  

National Technical Information Service (NTIS)

A left-handed composite material which includes a mixture of a ferromagnetic material and a dielectric material. The direction of magnetization of the ferromagnetic material, and its volume fraction are controlled such that the composite material exhibits...

J. Q. Xiao S. T. Chui

2003-01-01

46

Multilayer Electroactive Polymer Composite Material  

NASA Technical Reports Server (NTRS)

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2011-01-01

47

The nature and composition of amorphous material and free oxides in some temperate region and tropical soils  

Microsoft Academic Search

Amorphous clay separated from pedons of a highly weathered soil previously classified as Oxisol and an Ultisol of the Southern States and, from the surface horizons of an Oxisol and two Andepts of the tropics were studied by chemical, DTA, infrared and X?ray analysis.Considerable amounts of amorphous material, 2037% in temperate region and 2940% in tropical soils, were extracted by

K. H. Tan; H. F. Perkins; R. A. McCreery

1970-01-01

48

Ski Technology And Composite Materials  

NSDL National Science Digital Library

The following resource is from Lessonopoly, which has created student activities and lesson plans to support the video series, Science of the Olympic Winter Games, created by NBC Learn and the National Science Foundation. Featuring exclusive footage from NBC Sports and contributions from Olympic athletes and NSF scientists, the series will help teach your students valuable scientific concepts. Students will learn the basic engineering issues related to ski design. They will learn about composite materials and polymer materials. Also, students will create and test a composite material.

2010-01-01

49

Birefringent nanostructured composite materials  

NASA Astrophysics Data System (ADS)

We use a very efficient recursive method to calculate the effective optical response of materials made up of arbitrarily shaped dielectric inclusions arranged in periodic 2D arrays within a metal matrix with a lattice constant much smaller than the wavelength of the incident light, so that we may neglect retardation. The starting point of the calculation is a digitized image of the system. The geometrical shape of the inclusions and their orientation in the 2D array induce a birefringent optical response of the whole metamaterial that can be tailored to specific needs.

Mendoza, Bernardo S.; Mochn, W. Luis

2012-03-01

50

Nanophase and Composite Optical Materials  

NASA Technical Reports Server (NTRS)

This talk will focus on accomplishments, current developments, and future directions of our work on composite optical materials for microgravity science and space exploration. This research spans the order parameter from quasi-fractal structures such as sol-gels and other aggregated or porous media, to statistically random cluster media such as metal colloids, to highly ordered materials such as layered media and photonic bandgap materials. The common focus is on flexible materials that can be used to produce composite or artificial materials with superior optical properties that could not be achieved with homogeneous materials. Applications of this work to NASA exploration goals such as terraforming, biosensors, solar sails, solar cells, and vehicle health monitoring, will be discussed.

2003-01-01

51

Method for making composite material  

US Patent & Trademark Office Database

A method for fabricating a composite material includes providing a free-standing carbon nanotube structure having a plurality of carbon nanotubes, introducing at least two reacting materials into the carbon nanotube structure to form a reacting layer, activating the reacting materials to grow a plurality of nanoparticles, wherein the nanoparticles are spaced from each other and coated on a surface of each of the carbon nanotubes of the carbon nanotube structure.

2012-10-30

52

Composite material impregnation unit  

NASA Technical Reports Server (NTRS)

This memorandum presents an introduction to the NASA multi-purpose prepregging unit which is now installed and fully operational at the Langley Research Center in the Polymeric Materials Branch. A description of the various impregnation methods that are available to the prepregger are presented. Machine operating details and protocol are provided for its various modes of operation. These include, where appropriate, the related equations for predicting the desired prepreg specifications. Also, as the prepregger is modular in its construction, each individual section is described and discussed. Safety concerns are an important factor and a chapter has been included that highlights the major safety features. Initial experiences and observations for fiber impregnation are described. These first observations have given great insight into the areas of future work that need to be addressed. Future memorandums will focus on these individual processes and their related problems.

Wilkinson, S. P.; Marchello, J. M.; Johnston, N. J.

1993-01-01

53

Estimating the molecular composition of a diverse range of natural organic materials from solid-state 13 C NMR and elemental analyses  

Microsoft Academic Search

Most techniques for determining the chemical nature of natural organic matter in soil, sediment and water require prior extraction or concentration steps that are not quantitative and that create artifacts. 13C nuclear magnetic resonance (NMR) analysis can avoid these problems, but it gives little information at the scale of molecules. Here we show that the molecular composition of a diverse

Paul N. Nelson; Jeffrey A. Baldock

2005-01-01

54

Energy Absorption of Composite Materials  

Microsoft Academic Search

This paper presents results of a study on the energy absorption characteristics of selected composite material systems and compares the results with aluminum. Com posite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite\\/epoxy (Gr\\/E), Kevlar epoxy (K\\/E) and glass\\/epoxy (Gl\\/E). Chamfering and notching one end of the composite tube specimen reduced the peak load

Gary L. Farley

1983-01-01

55

Dense, finely, grained composite materials  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

56

Fracture problems in composite materials  

NASA Technical Reports Server (NTRS)

A series of fracture problems in composite materials are identified, their methods of solution are briefly discussed, and some sample results are presented. The main problem of interest is the determination of the stress state in the neighborhood of localized imperfections such as cracks and inclusions which may exist in the composite. Particular emphasis is placed on the evaluation of quantities such as the stress intensity factors, the power of the stress singularity, and the strain energy release rate, which may be used directly or indirectly in connection with an appropriate fracture criterion for the prediction of fracture initiation and propagation load levels. The topics discussed include a crack in layered composites, a crack terminating at and going through a bi-material interface, a penny-shaped crack in a filament-reinforced elastic matrix, and inclusion problems in bonded materials.

Erdogan, F.

1972-01-01

57

Impact response of composite materials  

NASA Technical Reports Server (NTRS)

Composite materials composed of carbon fibers and resin matrices offer great promise in reducing the weight of aerospace structures. However they remain extremely vulnerable to out of plane impact loads, which lead to severe losses in strength and stiffness. The results of an experimental program, undertaken to investigate the low velocity impact damage tolerance of composite materials is presented. The objectives were to identify key neat resin/composite properties that lead to enhancement of composite impact damage tolerance and to find a small scale test that predicts compression after impact properties of panels. Five materials were selected for evaluation. These systems represented different classes of material behavior such as brittle epoxy, modified epoxies, and amorphous and semicrystalling thermoplastics. The influence of fiber properties on the impact performance was also studied in one material, i.e., in polyether ether ketone (PEEK). Several 24 and 48 ply quasi-isotropic and 24 ply orthotropic laminates were examined using an instrumented drop weight impactor. Correlations with post impact compression behavior were made.

Tiwari, S. N.; Srinivasan, K.

1991-01-01

58

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

Research related to growth of an imbedded through-width delamination (ITWD) in a compression loaded composite structural element is presented. Composites with widely different interlaminar fracture resistance were examined, viz., graphite/epoxy (CYCOM 982) and graphite/PEEK (APC-2). The initial part of the program consisted of characterizing the material in tension, compression and shear mainly to obtain consistent material properties for analysis, but also as a check of the processing method developed for the thermoplastic APC-2 material. The characterization of the delamination growth in the ITWD specimen, which for the unidirectional case is essentially a mixed Mode 1 and 2 geometry, requires verified mixed-mode growth criteria for the two materials involved. For this purpose the main emphasis during this part of the investigation was on Mode 1 and 2 fracture specimens, namely the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimens.

Gillespie, J. W., Jr.; Carlson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1985-01-01

59

Welds in thermoplastic composite materials  

Microsoft Academic Search

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

N. S. Taylor

1990-01-01

60

Welds in thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Taylor, N. S.

61

Durability of polymer composite materials  

Microsoft Academic Search

The purpose of this research is to examine structural durability of advanced composite materials under critical loading conditions, e.g., combined thermal and mechanical loading and shear fatigue loading. A thermal buckling model of a burnt column, either axially restrained or under an axial applied force was developed. It was predicted that for a column exposed to the high heat flux

Liu Liu

2006-01-01

62

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

Micromechanical Combined Stress Analysis (MICSTRAN) computer code provides materials engineers with easy-to-use personal-computer-based software tool to calculate overall properties of composite, given properties of fibers and matrix. Computes overall thermoelastic parameters and stresses by micromechanical analysis. Written in FORTRAN 77.

Naik, Rajiv A.

1994-01-01

63

Composite Materials: An Educational Need.  

ERIC Educational Resources Information Center

Described is the need to incorporate the concepts and applications of advanced composite materials into existing chemical engineering programs. Discussed are the justification for, and implementation of topics including transport phenomena, kinetics and reactor design, unit operations, and product and process design. (CW)

Saliba, Tony E.; Snide, James A.

1990-01-01

64

Energy absorption of composite materials  

NASA Technical Reports Server (NTRS)

Results of a study on the energy absorption characteristics of selected composite material systems are presented and the results compared with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite/epoxy (Gr/E), Kevlar (TM)/epoxy (K/E) and glass/epoxy (Gl/E). Chamfering and notching one end of the composite tube specimen reduced the peak load at initial failure without altering the sustained crushing load, and prevented catastrophic failure. Static compression and vertical impact tests were performed on 128 tubes. The results varied significantly as a function of material type and ply orientation. In general, the Gr/E tubes absorbed more energy than the Gl/E or K/E tubes for the same ply orientation. The 0/ + or - 15 Gr/E tubes absorbed more energy than the aluminum tubes. Gr/E and Gl/E tubes failed in a brittle mode and had negligible post crushing integrity, whereas the K/E tubes failed in an accordian buckling mode similar to the aluminum tubes. The energy absorption and post crushing integrity of hybrid composite tubes were not significantly better than that of the single material tubes.

Farley, G. L.

1983-01-01

65

Fractal nature of humic materials  

SciTech Connect

Fractals are geometric representatives of strongly disordered systems whose structure is described by nonintegral dimensions. A fundamental tenet of fractal geometry is that disorder persists at any characterization scale-length used to describe the system. The nonintegral nature of these fractal dimensions is the result of the realization that a disordered system must possess more structural detail than an ordered system with classical dimensions of 1, 2, or 3 in order to accommodate this disorder within disorder.'' Thus from a fractal perspective, disorder is seen as an inherent characteristic of the system rather than as a perturbative phenomena forced upon it. Humic materials are organic substances that are formed by the profound alteration of organic matter in a natural environment. They can be operationally divided into 3 fractions; humic acid (soluble in base), fulvic acid (soluble in acid or base), and humin (insoluble in acid or base). Each of these fraction has been shown to be an extremely heterogeneous mixture. These mixtures have proven so intractable that they may represent the ultimate in molecular disorder. In fact, based on the characteristics that humic materials must possess in order to perform their functions in natural systems, it has been proposed that the fundamental chemical characteristic of a humic material is not a discrete chemical structure but a pronounced lack of order on a molecular level. If the fundamental chemical characteristic of a humic material is a strongly disordered nature, as has been proposed, then humic materials should be amenable to characterization by fractal geometry. The purpose of this paper is to test this hypothesis.

Rice, J.A. (South Dakota State Univ., Brookings, SD (United States). Dept. of Chemistry); Lin, J.S. (Oak Ridge National Lab., TN (United States))

1992-01-01

66

Fractal nature of humic materials  

SciTech Connect

Fractals are geometric representatives of strongly disordered systems whose structure is described by nonintegral dimensions. A fundamental tenet of fractal geometry is that disorder persists at any characterization scale-length used to describe the system. The nonintegral nature of these fractal dimensions is the result of the realization that a disordered system must possess more structural detail than an ordered system with classical dimensions of 1, 2, or 3 in order to accommodate this ``disorder within disorder.`` Thus from a fractal perspective, disorder is seen as an inherent characteristic of the system rather than as a perturbative phenomena forced upon it. Humic materials are organic substances that are formed by the profound alteration of organic matter in a natural environment. They can be operationally divided into 3 fractions; humic acid (soluble in base), fulvic acid (soluble in acid or base), and humin (insoluble in acid or base). Each of these fraction has been shown to be an extremely heterogeneous mixture. These mixtures have proven so intractable that they may represent the ultimate in molecular disorder. In fact, based on the characteristics that humic materials must possess in order to perform their functions in natural systems, it has been proposed that the fundamental chemical characteristic of a humic material is not a discrete chemical structure but a pronounced lack of order on a molecular level. If the fundamental chemical characteristic of a humic material is a strongly disordered nature, as has been proposed, then humic materials should be amenable to characterization by fractal geometry. The purpose of this paper is to test this hypothesis.

Rice, J.A. [South Dakota State Univ., Brookings, SD (United States). Dept. of Chemistry; Lin, J.S. [Oak Ridge National Lab., TN (United States)

1992-03-01

67

Characterization of natural fiber surfaces and natural fiber composites  

Microsoft Academic Search

Experiments have been performed to further the development of natural fiber reinforced composites as a replacement for glass fiber composites. Untreated and treated surfaces of natural fibers were characterized using FTIR, XPS, and ESEM. Changes in the peaks in the FTIR spectrum at 1730, 1625 and 1239cm?1 indicated that the alkali treatment removes hemicellulose and lignin from natural fiber surfaces.

N. Sgriccia; M. C. Hawley; M. Misra

2008-01-01

68

Nature of the ``Orange'' Material on Vesta from Dawn  

NASA Astrophysics Data System (ADS)

The Dawn mission revealed distinct units on Vesta with red spectral slope. Oppia ejecta is identified as Leslie unit" postulated by Gaffey (1997). Orange material composition is unlikely to be metal or olivine. Its nature is most likely impact melt.

Le Corre, L.; Reddy, V.; Schmedemann, N.; Becker, K. J.; O'Brien, D. P.; Yamashita, N.; Peplowski, P. N.; Prettyman, T. H.; Li, J.-Y.; Cloutis, E. A.; Denevi, B. W.; Kneissl, T.; Palmer, E.; Gaskell, R. W.; Nathues, A.; Gaffey, M. J.; Mittlefehldt, D. W.; Gary, W. B.; Sierks, H.; Russell, C. T.; Raymond, C. A.

2014-02-01

69

Sunflower cake as a natural composite: composition and plastic properties.  

PubMed

Nowadays, the end-of-life of plastic products and the decrease of fossil energy are great environmental problems. Moreover, with the increase of food and nonfood transformations of renewable resources, the quantities of agro-industrial byproducts and wastes increase hugely. These facts allow the development of plastic substitutes made from agro-resources. Many researches show the feasibility of molding biopolymers extracted from plants like a common polymeric matrix. Other natural macromolecules are used like fillers into polyolefins, for example. However, limited works present results about the transformation of a natural blend of biopolymers into a plastic material. The aim of this study is the determination of the composition of sunflower cake (SFC) and also the characterization of its components. These were identified by chemical and biochemical analysis often used in agricultural or food chemistry. Most of the extraction and purification processes modify the macrostructure of several biopolymers (e.g., denaturation of proteins, cleavage or creation of weak bonds, etc.). So, the composition of different parts of the sunflower seed (husk, kernel, and also protein isolate) was determined, and the plasticlike properties of their components were studied with thermogravimetric analysis, differential scanning calorimetry, and a dynamic mechanical thermal analysis apparatus. Finally, this indirect way of characterization showed that SFC can be considered a natural composite. In SFC, several components like lignocellulosic fibers [40%/dry matter (DM)], which essentially come from the husk of sunflower seed, can act as fillers. However, other biopolymers like globulins ( approximately 30% of the 30% of sunflower seed proteins/DM of SFC) can be shaped as a thermoplastic-like material because this kind of protein has a temperature of glass transition and a temperature of denaturation that seems to be similar to a melting temperature. These proteins have also viscoelastic properties. Moreover, SFC has similar rheological properties and other physicochemical properties compatible with shaping or molding behaviors of plastic-processing machinery. PMID:18998703

Geneau-Sbarta, Cline; Leyris, Juliette; Silvestre, Franoise; Rigal, Luc

2008-12-10

70

Offgassing Test Methodology for Composite Materials.  

National Technical Information Service (NTIS)

A significant increase in the use of composite materials has occurred during the past 20 years. Associated with this increased use is the potential for employees to be exposed to offgassing components from composite systems. Various components in composit...

D. A. Scheer

1994-01-01

71

NDE of polymeric composite material bridge components  

NASA Astrophysics Data System (ADS)

Rapid advancements with respect to utilization of polymeric composite materials for bridge components is occurring. This situation is driven primarily by the potential improvements offered by these materials with respect to long term durability. However, because of the developmental nature of these materials much of the materials characterization has involved short term testing without the synergistic effects of environmental exposure. Efforts to develop nondestructive evaluation procedures, essential for any wide spread use in critical structural applications, have been consequently limited. This paper discuses the effort to develop NDE methods for field inspection of hybrid glass and carbon fiber reinforced vinyl ester pultruded 'double box' I beams that are installed in a small bridge over Tom's Creek, in Blacksburg, Virginia. Integrated structural element sensors, dormant infrared devices, as well as acousto-ultrasonic methods are under development for detecting and monitoring the occurrence and progression of life limiting deterioration mechanisms.

Duke, John C.; Horne, Michael R.

1998-03-01

72

Health Hazards of Combustion Products from Aircraft Composite Materials.  

National Technical Information Service (NTIS)

Concerns about the potential health hazards of burning fiber-reinforced polymer composites in aircraft fires parallel the rising usage of these materials for commercial aircraft primary and secondary structures. An overview of the nature and the potential...

S. Gandhi R. E. Lyon

1998-01-01

73

Thermal Expansion Properties of Composite Materials.  

National Technical Information Service (NTIS)

Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, envi...

R. R. Johnson M. H. Kural G. B. Mackey

1981-01-01

74

Properties of composite materials for cryogenic applications  

Microsoft Academic Search

Composite materials are used in a wide variety of cryogenic applications because of their unique and highly tailorable properties. These cryogenic applications of composites may be, for the sake of discussion, classified as support structures, vessels, or electrical insulation. Examples of these applications are presented, with a brief discussion of the critical material properties associated with each application. Composite material

J. B Schutz

1998-01-01

75

Composite materials for fusion applications  

SciTech Connect

Ceramic matrix composites, CMCs, are being considered for advanced first-wall and blanket structural applications because of their high-temperature properties, low neutron activation, low density and low coefficient of expansion coupled with good thermal conductivity and corrosion behavior. This paper presents a review and analysis of the hermetic, thermal conductivity, corrosion, crack growth and radiation damage properties of CMCs. It was concluded that the leak rates of a gaseous coolant into the plasma chamber or tritium out of the blanket could exceed design criteria if matrix microcracking causes existing porosity to become interconnected. Thermal conductivities of unirradiated SiC/SiC and C/SiC materials are about 1/2 to 2/3 that of Type 316 SS whereas the thermal conductivity for C/C composites is seven times larger. The thermal stress figure-of-merit value for CMCs exceeds that of Type 316 SS for a single thermal cycle. SiC/SiC composites are very resistant to corrosion and are expected to be compatible with He or Li coolants if the O{sub 2} concentrations are maintained at the appropriate levels. CMCs exhibit subcritical crack growth at elevated temperatures and the crack velocity is a function of the corrosion conditions. The radiation stability of CMCs will depend on the stability of the fiber, microcracking of the matrix, and the effects of gaseous transmutation products on properties. 23 refs., 14 figs., 1 tab.

Jones, R.H.; Henager, C.H. Jr.; Hollenberg, G.W.

1991-10-01

76

Composite materials for thermal energy storage  

DOEpatents

The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, David K. (Golden, CO); Burrows, Richard W. (Conifer, CO); Shinton, Yvonne D. (Northglenn, CO)

1986-01-01

77

A new approach for modeling composite materials  

NASA Astrophysics Data System (ADS)

The increasing use of composite materials is due to their ability to tailor materials for special purposes, with applications evolving day by day. This is why predicting the properties of these systems from their constituents, or phases, has become so important. However, assigning macroscopical optical properties for these materials from the bulk properties of their constituents is not a straightforward task. In this research, we present a spectral analysis of three-dimensional random composite typical nanostructures using an Extension of the Discrete Dipole Approximation (E-DDA code), comparing different approaches and emphasizing the influences of optical properties of constituents and their concentration. In particular, we hypothesize a new approach that preserves the individual nature of the constituents introducing at the same time a variation in the optical properties of each discrete element that is driven by the surrounding medium. The results obtained with this new approach compare more favorably with the experiment than previous ones. We have also applied it to a non-conventional material composed of a metamaterial embedded in a dielectric matrix. Our version of the Discrete Dipole Approximation code, the EDDA code, has been formulated specifically to tackle this kind of problem, including materials with either magnetic and tensor properties.

Alcaraz de la Osa, R.; Moreno, F.; Saiz, J. M.

2013-03-01

78

Estimating Weibull parameters for composite materials.  

NASA Technical Reports Server (NTRS)

This paper deals with the statistical analysis of strength and fracture of materials in general, with application to fiber composites. The 'weakest link' model is considered in a fairly general form, and the resulting equations are demonstrated by using a Weibull distribution for flaws. This distribution appears naturally in a variety of problems, and therefore additional attention is devoted to analysis and statistical estimation connected with this distribution. Special working charts are included to facilitate interpretation of observed data and estimation of parameters. Implications of the size effect are considered for various kinds of flaw distributions. The paper describes failure and damage in a fiber-reinforced systems.

Robinson, E. Y.

1972-01-01

79

Space processing of composite materials  

NASA Technical Reports Server (NTRS)

Materials and processes for the testing of aluminum-base fiber and particle composites, and of metal foams under extended-time low-g conditions were investigated. A wetting and dispersion technique was developed, based on the theory that under the absence of a gas phase all solids are wetted by liquids. The process is characterized by a high vacuum environment and a high temperature cycle. Successful wetting and dispersion experiments were carried out with sapphire fibers, whiskers and particles, and with fibers of silicon carbide, pyrolytic graphite and tungsten. The developed process and facilities permit the preparation of a precomposite which serves as sample material for flight experiments. Low-g processing consists then merely in the uniform redistribution of the reinforcements during a melting cycle. For the preparation of metal foams, gas generation by means of a thermally decomposing compound was found most adaptable to flight experiments. For flight experiments, the use of compacted mixture of the component materials limits low-g processing to a simple melt cycle.

Steurer, W. H.; Kaye, S.

1975-01-01

80

Composite materials for thermal energy storage  

NASA Astrophysics Data System (ADS)

A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations are discussed. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, D. K.; Burrows, R. W.; Shinton, Y. D.

1985-01-01

81

Composite materials for thermal energy storage  

DOEpatents

A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

1985-01-04

82

Material awareness on natural feeding.  

PubMed

introduction. Natural breastfeeding is the only proper way to feed newborns and infants because it ensures their proper development. Breastfeeding enhances health and protects against the development of many diseases in childhood and adulthood. The primary benefits of breastfeeding include reduced incidences of infection in the respiratory system as well as a reduction in gastrointestinal and systemic infections. The benefits of breastfeeding also include decreased inflammation and improved immunity to disease in the infant. Further benefits of breastfeeding are reduced incidences of type 1 diabetes, Crohn's disease, and rheumatoid arthritis. objective. The aim of the study was to assess the degree of knowledge on maternal breastfeeding among current expecting mothers. materials and method. The study comprtisded 147 mothers hospitalized in the Gynecology-Obstetrics Hospital University of Medical Sciences in Pozna?, Poland, during late July - August 2012. results. For 139 (93.88%) of the surveyed women, breastfeeding was a priority regarding the health of the child. Respondents most often used professional literature in order to gain knowledge about breastfeeding (63.27%). The least popular way of acquiring knowledge was through the media (27.21%). conclusions. Analysis of the collected material on the surveyed women showed that women have a diverse range of knowledge about breastfeeding. Currently, breastfeeding is required to be promoted and supported by midwives, paediatricians and other health professionals. PMID:24959806

Plagens-Rotman, Katarzyna; Kubiak, S?awomira; Pi?ta, Beata; Wszo?ek, Katarzyna; Iwanowicz-Palus, Gra?yna; Opala, Tomasz

2014-06-10

83

Accelerated Aging of Polymer Composite Bridge Materials.  

National Technical Information Service (NTIS)

Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine co...

1999-01-01

84

The nature of cometary materials  

NASA Technical Reports Server (NTRS)

Because cometary surfaces are likely to be far colder and of a different composition than planetary surfaces, there are some new considerations that must be examined in regards to placing instrumented packages or sample return devices on their surfaces. The qualitative analysis of the problem of attaching hardware to a comet and not being ejected back into space can be divided into two parts. The first problem is to pierce the mantle and obtain access to the icy core. Drilling through the mantle requires that the drilling forces be reacted. Reacting such forces probably requires attachment to the icy core below. Therefore, some kinetic impact piercing device is likely to be required as the first act of attachment. The second problem for a piercing device to overcome is the force produced by the impact kinetic energy that tries to eject the piercing device back into space. The mantle and icy core can absorb some of the impact kinetic energy in the form of fracture formation and friction energy. The energy that is not absorbed in these two ways is stored by the core as elastic deformation of the mantle and icy core. It is concluded that because the cometary materials are almost certainly brittle and the icy core is likely to be self lubricating, the elastic rebound and gas pressure expulsion forces must be counteracted by forces greater than those that may be provided by a piercing device or its capture devices (barbs).

Stephens, James

1989-01-01

85

Microbial growth on fiber reinforced composite materials  

Microsoft Academic Search

Microorganisms may be responsible for physical and chemical changes in composite materials. Inoculation of a fungal consortium to pre-sterilized coupons of five composites resulted in deep penetration into the interior of all materials at a temperature of approximately 22C within 5 weeks. Scanning electron microscopy (SEM) showed that the inoculated composites were etched by the microorganisms. None of the five

Ji-Dong Gu; T. Ford; K. Thorp; R. Mitchell

1996-01-01

86

Composite materials for space structures  

NASA Technical Reports Server (NTRS)

The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

1985-01-01

87

Thin film dielectric composite materials  

DOEpatents

A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

Jia, Quanxi (Los Alamos, NM) [Los Alamos, NM; Gibbons, Brady J. (Los Alamos, NM) [Los Alamos, NM; Findikoglu, Alp T. (Los Alamos, NM) [Los Alamos, NM; Park, Bae Ho (Los Alamos, NM) [Los Alamos, NM

2002-01-01

88

Air Force requirements for NDE of composite materials  

Microsoft Academic Search

The usage of composite materials has increased and continues to grow in advanced and sophisticated weapon systems. The complexity of structures, and the need for rapid inspection and assessment of systems require further development of existing inspection methods to provide the accuracy and reliability desired. Because of the inherently anisotropic and sometimes nonuniform layered nature of composites, detection and interpretation

T. M. Cordell; P. K. Bhagat

1991-01-01

89

New Armour Materials: Metal Matrix Composites.  

National Technical Information Service (NTIS)

The ballistic properties of metal matrix composites are reviewed and discussed. All the data located treats aluminum-base composites reinforced with silicon carbide, boron carbide or aluminum oxide particles. Most of these materials have not been optimize...

S. J. Savage

1994-01-01

90

Spectroscopy of MPS(3):DAMS(+) composite materials  

NASA Astrophysics Data System (ADS)

Composite materials are comprised of two separate components that are brought together to form a new material that exhibits unique properties not found in the individual components. The composite material studied in this work is a guest dye cation, (4-[4-(dimethylamino)-alpha-styrl]-1-methylpyridinium) or DAMS+, intercalated into an inorganic host lattice (MPS 3, where M = Cd2+ or Mn2+). MPS3 :DAMS+ exhibits high-efficiency second-harmonic generation (SHG), which is only observed when a material lacks a center of symmetry. There must be an organization of dye molecules upon intercalation to induce the noncentrosymmetry necessary for SHG. The formation of dye aggregates will be studied as a possible noncentrosymmetric arrangement. The intercalated materials (MPS3:DAMS+) exhibited spectral features of J-aggregates. These features included a sharp aggregate absorption and emission band, known as the J-band. There was a small Stokes shift (250 cm-1) between aggregate absorption and emission bands, and a red-shift between the J-band and isolated dye absorption band (3,700 cm-1). The low-energy tail of the emission J-band was theoretically modeled using the Urbach-Martienssen equation, while the high-energy states were fit to a Gaussian to determine aggregate disorder. Disorder was also modeled using a Monte-Carlo lineshape analysis program. From these theoretical models, the aggregate was found to be two-dimensional and weakly coupled. A variety of sample types were studied including intercalated powders and single crystals using absorbance, reflectance and emission spectroscopy. Reflectance spectra were directly compared with absorbance spectra using the Kramers-Kronig Transformation2 to determine that the surface aggregates and the interior aggregates were structurally similar. A new imaging microspectrophotometer was developed to investigate the topology of the composite materials. Kinetics of the intercalation front were studied and a layer-by-layer intercalation mechanism was developed. Surface studies using other materials indicated the polyanion nature of MPS3 :DAMS+ was essential for aggregation. Infrared microspectroscopy was used to determine the orientation of dye molecules on the surface of the large composite crystals. The DAMS+ in MPS 3:DAMS+ was shown to form two-dimensional brickwork aggregates with the molecules aligned "edge-on" on the surface and interior of the host lattice.

Holt, Jennifer Suzanne

91

Morphology and microstructure of composite materials  

NASA Technical Reports Server (NTRS)

Lightweight continuous carbon fiber based polymeric composites are currently enjoying increasing acceptance as structural materials capable of replacing metals and alloys in load bearing applications. As with most new materials, these composites are undergoing trials with several competing processing techniques aimed at cost effectively producing void free consolidations with good mechanical properties. As metallic materials have been in use for several centuries, a considerable database exists on their morphology - microstructure; and the interrelationships between structure and properties have been well documented. Numerous studies on composites have established the crucial relationship between microstructure - morphology and properties. The various microstructural and morphological features of composite materials, particularly those accompanying different processing routes, are documented.

Tiwari, S. N.; Srinivansan, K.

1991-01-01

92

NASA technology utilization survey on composite materials  

NASA Technical Reports Server (NTRS)

NASA and NASA-funded contractor contributions to the field of composite materials are surveyed. Existing and potential non-aerospace applications of the newer composite materials are emphasized. Economic factors for selection of a composite for a particular application are weight savings, performance (high strength, high elastic modulus, low coefficient of expansion, heat resistance, corrosion resistance,), longer service life, and reduced maintenance. Applications for composites in agriculture, chemical and petrochemical industries, construction, consumer goods, machinery, power generation and distribution, transportation, biomedicine, and safety are presented. With the continuing trend toward further cost reductions, composites warrant consideration in a wide range of non-aerospace applications. Composite materials discussed include filamentary reinforced materials, laminates, multiphase alloys, solid multiphase lubricants, and multiphase ceramics. New processes developed to aid in fabrication of composites are given.

Leeds, M. A.; Schwartz, S.; Holm, G. J.; Krainess, A. M.; Wykes, D. M.; Delzell, M. T.; Veazie, W. H., Jr.

1972-01-01

93

Composite structural materials. [fiber reinforced composites for aircraft structures  

NASA Technical Reports Server (NTRS)

Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1981-01-01

94

Advanced Composite Materials for Precision Segmented Reflectors.  

National Technical Information Service (NTIS)

The objective in the NASA Precision Segmented Reflector (PSR) project is to develop new composite material concepts for highly stable and durable reflectors with precision surfaces. The project focuses on alternate material concepts such as the developmen...

B. A. Stein D. E. Bowles

1988-01-01

95

New Textile Composite Materials Development, Production, Application.  

National Technical Information Service (NTIS)

New textile composite materials development, production, and application are discussed. Topics covered include: super-high-strength, super-high-modulus fibers, filaments, and materials manufactured on their basis; heat-resistant and nonflammable fibers, f...

P. Y. Mikhailov

1993-01-01

96

Overview of bacterial cellulose composites: a multipurpose advanced material.  

PubMed

Bacterial cellulose (BC) has received substantial interest owing to its unique structural features and impressive physico-mechanical properties. BC has a variety of applications in biomedical fields, including use as biomaterial for artificial skin, artificial blood vessels, vascular grafts, scaffolds for tissue engineering, and wound dressing. However, pristine BC lacks certain properties, which limits its applications in various fields; therefore, synthesis of BC composites has been conducted to address these limitations. A variety of BC composite synthetic strategies have been developed based on the nature and relevant applications of the combined materials. BC composites are primarily synthesized through in situ addition of reinforcement materials to BC synthetic media or the ex situ penetration of such materials into BC microfibrils. Polymer blending and solution mixing are less frequently used synthetic approaches. BC composites have been synthesized using numerous materials ranging from organic polymers to inorganic nanoparticles. In medical fields, these composites are used for tissue regeneration, healing of deep wounds, enzyme immobilization, and synthesis of medical devices that could replace cardiovascular and other connective tissues. Various electrical products, including biosensors, biocatalysts, E-papers, display devices, electrical instruments, and optoelectronic devices, are prepared from BC composites with conductive materials. In this review, we compiled various synthetic approaches for BC composite synthesis, classes of BC composites, and applications of BC composites. This study will increase interest in BC composites and the development of new ideas in this field. PMID:24053844

Shah, Nasrullah; Ul-Islam, Mazhar; Khattak, Waleed Ahmad; Park, Joong Kon

2013-11-01

97

Optical Characterization of Semiconducting Natural Rubber Nanoparticles and its Composites  

NASA Astrophysics Data System (ADS)

The present work explains optical properties of semiconducting natural rubber nanoparticles from pristine natural rubber by doping. The studies give evidence that the SbCl5 is an efficient dopant for natural rubber. The mechanism of conduction predominantly involves the formation of conjugated sequence of unsaturated double bond in the polymer backbone. Examination of the UV/Vis study reveals the formation of charge transfer complexes in the polymer back bone. Particle filled elastomeric composites have become attractive owing to their low cost and widespread industrial applications. The arrival of nanometer fillers to polymer materials is a promising channel for their property modification. Natural rubber composite is prepared by mixing the pristine natural rubber with semiconducting natural rubber powder.

Neena, P.; Mathew, Anisha Mary

2011-10-01

98

Tough composite materials: Recent developments  

NASA Technical Reports Server (NTRS)

The present volume broadly considers topics in composite fracture toughness and impact behavior characterization, composite system constituent properties and their interrelationships, and matrix systems' synthesis and characterization. Attention is given to the characterization of interlaminar crack growth in composites by means of the double cantilever beam specimen, the characterization of delamination resistance in toughened resin composites, the effect of impact damage and open holes on the compressive strength of tough resin/high strain fiber laminates, the effect of matrix and fiber properties on compression failure mechanisms and impact resistance, the relation of toughened neat resin properties to advanced composite mechanical properties, and constituent and composite properties' relationships in thermosetting matrices. Also treated are the effect of cross-link density on the toughening mechanism of elastomer-modified epoxies, the chemistry of fiber/resin interfaces, novel carbon fibers and their properties, the development of a heterogeneous laminating resin, solvent-resistant thermoplastics, NASA Lewis research in advanced composites, and opportunities for the application of composites in commercial aircraft transport structures.

Vosteen, L. F. (editor); Johnston, N. J. (editor); Teichman, L. A. (editor); Blankenship, C. P. (editor)

1985-01-01

99

Composite materials and method of making  

DOEpatents

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

100

Flame-retardant composite materials  

NASA Technical Reports Server (NTRS)

The properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: VPSP/BMI, a blend of vinylpolystyryl pyridine and bismaleimide; BMI, a bismaleimide; and phenolic and PSP, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that VPSP/BMI with the graphite tape was the optimum design giving the lowest heat release rate.

Kourtides, Demetrius A.

1991-01-01

101

Flame-Retardant Composite Materials.  

National Technical Information Service (NTIS)

The properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: VPSP/BMI, a blend of vinylpolystyryl pyridine and bismaleimide; ...

D. A. Kourtides

1991-01-01

102

New textile composite materials development, production, application  

NASA Technical Reports Server (NTRS)

New textile composite materials development, production, and application are discussed. Topics covered include: super-high-strength, super-high-modulus fibers, filaments, and materials manufactured on their basis; heat-resistant and nonflammable fibers, filaments, and textile fabrics; fibers and textile fabrics based on fluorocarbon poylmers; antifriction textile fabrics based on polyfen filaments; development of new types of textile combines and composite materials; and carbon filament-based fabrics.

Mikhailov, Petr Y.

1993-01-01

103

Advanced composites: Environmental effects on selected resin matrix materials  

NASA Technical Reports Server (NTRS)

The effects that expected space flight environment has upon the mechanical properties of epoxy and polyimide matrix composites were analyzed. Environmental phenomena covered water immersion, high temperature aging, humidity, lightning strike, galvanic action, electromagnetic interference, thermal shock, rain and sand erosion, and thermal/vacuum outgassing. The technology state-of-the-art for graphite and boron reinforced epoxy and polyimide matrix materials is summarized to determine the relative merit of using composites in the space shuttle program. Resin matrix composites generally are affected to some degree by natural environmental phenomena with polyimide resin matrix materials less affected than epoxies.

Welhart, E. K.

1976-01-01

104

Combinatorial synthesis of inorganic or composite materials  

DOEpatents

Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials or, alternatively, allowing the components to interact to form at least two different materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, nonbiological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

Goldwasser, Isy (Palo Alto, CA); Ross, Debra A. (Mountain Ranch, CA); Schultz, Peter G. (La Jolla, CA); Xiang, Xiao-Dong (Danville, CA); Briceno, Gabriel (Baldwin Park, CA); Sun, Xian-Dong (Fremont, CA); Wang, Kai-An (Cupertino, CA)

2010-08-03

105

Spectral representation theory of graded composite materials  

NASA Astrophysics Data System (ADS)

In graded composite materials, the physical properties can vary continuously in space and it may give different physical phenomena when compared with homogeneous materials. The Bergman-Milton spectral representation is a rigorous mathematical formalism to express the effective dielectric constant of nongraded composite materials [1]. In this study, we consider a material (rather than microsture [2]) graded composites, and generalize the Bergman-Milton spectral representation to extract the spectral density function for the effective dielectric constant of this graded composite material in the frequency domain [3]. Analytic and numerical solution will be presented for graded films and graded spheres. [1] D. J. Bergman, Phys. Rev. B 14, 4304 (1976). [2] J. P. Huang, K. W. Yu, G. Q. Gu, M. Karttunen, Phys. Rev. E 67, 051405 (2003). [3] L. Gao, J. P. Huang, K.W. Yu, Eur. Phys. J. B 36, 475 (2003).

Chan, K. L.; Kwok, C. M.; Yu, K. W.

2008-03-01

106

Graphene-based Composite Materials  

NASA Astrophysics Data System (ADS)

We investigated the mechanical properties, such as fracture toughness (KIc), fracture energy (GIc), ultimate tensile strength (UTS), Youngs modulus (E), and fatigue crack propagation rate (FCPR) of epoxy-matrix composites with different weight fractions of carbon-based fillers, including graphene platelets (GPL), graphene nanoribbons (GNR), single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT), and fullerenes (C60). Only 0.125 wt.% GPL was found to increase the KIc of the pure epoxy by 65% and the GIc by 115%. To get similar improvement, CNT and nanoparticle epoxy composites required one to two orders of magnitude greater weight fraction of nanofillers. Moreover, 0.125% wt.% GPL also decreased the fatigue crack propagation rate in the epoxy by 30-fold. The E value of 0.1 wt.% GPL/epoxy nanocomposite was 31% larger than the pure epoxy while there was only an increase of 3% for the SWNT composites. The UTS of the pristine epoxy was improved by 40% with GPLs in comparison with 14% enhancement for the MWNTs. The KIc of the GPL nanocomposite enhanced by 53% over the pristine epoxy compared to a 20% increase for the MWNT-reinforced composites. The results of the FCPR tests for the GPL nanocomposites showed a different trend. While the CNT nanocomposites were not effective enough to suppress the crack growth at high values of the stress intensity factor (DeltaK), the reverse behavior is observed for the GPL nanocomposites. The advantage of the GPLs over CNTs in terms of mechanical properties enhancement is due to their enormous specific surface area, enhanced adhesion at filler/epoxy interface (because of the wrinkled surfaces of GPLs), as well as the planar structure of the GPLs. We also show that unzipping of MWNTs into graphene nanoribbons (GNRs) enhances the load transfer effectiveness in epoxy nanocomposites. For instance, at 0.3 wt.% of fillers, the Young's modulus (E) of the epoxy nanocomposite with GNRs increased by 30% compared to their MWNTs counterpart. The ultimate tensile strength (UTS) for 0.3 wt.% GNR composites showed 22% enhancement compared to the MWNT composites at the same loading fraction of fillers (at 0.3 wt.%). Our results show that unzipping effect can be used to transform carbon nanotubes into graphene nanoribbons, which are far more effective than the baseline nanotube as a nanofiller in nanocomposites. The mechanical properties of fullerence (C60) epoxy nanocomposites at different loading fractions (wt.%) of fullerene fillers in the pristine epoxy was also studied. Fullerene (C60) fillers demonstrated good potential to improve the mechanical properties of epoxy composites. However the required C60 loading fractions were 1% which are still an order of magnitude higher than that for graphene platelets (0.1%). This again illustrates the superiority of graphene as a structural reinforcement additive for epoxy polymers at low nanofiller loadings. While the main focus of this work has been on epoxy polymers, initial results with ceramic matrix and metal (aluminum) matrix composites were also generated. These results demonstrate that GPL are highly effective in enahncing the fracture properties of silicon nitride ceramics. The fracture toughness of the baseline silicon nitride matrix increased by 235% (from 2.8 to 6.6 MPa.m1/2) at 1.5% GPL volume fraction. However the results were disappointing for aluminim matrix composites. Compared to the pure aluminum, the graphene-aluminum composites showed decreased strength and hardness. This is explained in the context of enhanced aluminum carbide formation with the graphene filler. These results indicate that Graphene Platelets (GPL) show strong potential as a nanofiller for epoxy nanocomposites and can provide a performance comparable to other forms of nanofillers at a significantly lower nanofiller loading fraction.

Rafiee, Mohammad Ali

107

Oxygen Compatibility Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

Composite materials offer significant weight-saving potential for aerospace applications in propellant and oxidizer tanks. This application for oxygen tanks presents the challenge of being oxygen compatible in addition to complying with the other required material characteristics. This effort reports on the testing procedures and data obtained in examining and selecting potential composite materials for oxygen tank usage. Impact testing of composites has shown that most of these materials initiate a combustion event when impacted at 72 ft-lbf in the presence of liquid oxygen, though testing has also shown substantial variability in reaction sensitivities to impact. Data for screening of 14 potential composites using the Bruceton method is given herein and shows that the 50-percent reaction frequencies range from 17 to 67 ft-lbf. The pressure and temperature rises for several composite materials were recorded to compare the energy releases as functions of the combustion reactions with their respective reaction probabilities. The test data presented are primarily for a test pressure of 300 psia in liquid oxygen. The impact screening process is compared with oxygen index and autogenous ignition test data for both the composite and the basic resin. The usefulness of these supplemental tests in helping select the most oxygen compatible materials is explored. The propensity for mechanical impact ignition of the composite compared with the resin alone is also examined. Since an ignition-free composite material at the peak impact energy of 72 ft-lbf has not been identified, composite reactivity must be characterized over the impact energy level and operating pressure ranges to provide data for hazard analyses in selecting the best potential material for liquid tank usage.

Engel, Carl D.; Watkins, Casey N.

2006-01-01

108

Acoustic Emission from Composite Materials.  

National Technical Information Service (NTIS)

The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique part...

I. C. Visconti R. Teti

1979-01-01

109

Advanced composite materials for precision segmented reflectors  

NASA Technical Reports Server (NTRS)

The objective in the NASA Precision Segmented Reflector (PSR) project is to develop new composite material concepts for highly stable and durable reflectors with precision surfaces. The project focuses on alternate material concepts such as the development of new low coefficient of thermal expansion resins as matrices for graphite fiber reinforced composites, quartz fiber reinforced epoxies, and graphite reinforced glass. Low residual stress fabrication methods will be developed. When coupon specimens of these new material concepts have demonstrated the required surface accuracies and resistance to thermal distortion and microcracking, reflector panels will be fabricated and tested in simulated space environments. An important part of the program is the analytical modeling of environmental stability of these new composite materials concepts through constitutive equation development, modeling of microdamage in the composite matrix, and prediction of long term stability (including viscoelasticity). These analyses include both closed form and finite element solutions at the micro and macro levels.

Stein, Bland A.; Bowles, David E.

1988-01-01

110

Instrumentation to Characterize Smart Materials and Composites.  

National Technical Information Service (NTIS)

Instrumentation was purchased through this DURIP grant to carry out experiments on shape memory alloys and smart composite structures. The ultimate objective is to develop reliable constitutive models for these advanced materials. this will involve carefu...

J. A. Shaw A. M. Waas

1999-01-01

111

Mechanics of Composite Materials for Spacecraft.  

National Technical Information Service (NTIS)

During this seven month project efforts continued on the development of advanced analytical and numerical techniques which can be effectively combined to provide advanced thermomechanical modeling of composite materials with nonlinear constituents. The ar...

G. J. Dvorak M. S. Shephard

1992-01-01

112

Composite Material Application to Liquid Rocket Engines  

NASA Technical Reports Server (NTRS)

The substitution of reinforced plastic composite (RPC) materials for metal was studied. The major objectives were to: (1) determine the extent to which composite materials can be beneficially used in liquid rocket engines; (2) identify additional technology requirements; and (3) determine those areas which have the greatest potential for return. Weight savings, fabrication costs, performance, life, and maintainability factors were considered. Two baseline designs, representative of Earth to orbit and orbit to orbit engine systems, were selected. Weight savings are found to be possible for selected components with the substitution of materials for metal. Various technology needs are identified before RPC material can be used in rocket engine applications.

Judd, D. C.

1982-01-01

113

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.

1981-01-01

114

Brittle Fracture Characteristics of Graphite/Epoxy Composites: Resistance to impact damage is related to construction geometry and nature of constituent materials.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A rpogram determined the mechanism of brittle impact fracture in an assortment of graphite/epoxy composites of various geometries. The influence of fiber and matrix ...

1981-01-01

115

Biomimicry of bamboo bast fiber with engineering composite materials  

Microsoft Academic Search

Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element,

S. H. Li; Q. Y. Zeng; Y. L. Xiao; S. Y. Fu; B. L. Zhou

1995-01-01

116

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement  

Microsoft Academic Search

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their

Deepaksh Gulati; Mohini Sain

2006-01-01

117

Stress waves in composite materials  

NASA Astrophysics Data System (ADS)

The method of cells (MOC) developed by Aboudi provides a powerful means for studying the propagation of waves through systems having complicated internal cell structure [

Wave Motion 9, 141 (1987)
]. Laminated materials are a common example. The method can handle harmonic waves and also transient waves arising from a finite duration impulse. The method is sufficiently robust to treat impact, as we show here. Both linear and nonlinear elastic-stress-strain relations can be included. The present work generalizes the method to include viscoelastic materials (such as polymers), systems with cell structure deviating from perfect periodicity (including random), and systems simulating actual impact experiments. We test the theory by comparing our results with measurements taken from a flat-plate impact experiment. The system investigated was a bilaminate composed of unit cells of epoxy and epoxy-graphite subcells. Using known and estimated material parameters, we find that the MOC gives a reasonable representation of the data. We then address some features of the experimental data that have not yet been explained by other theoretical methods. The importance of unit cell periodicity is tested by adding a random incremental width to each unit cell. Finally, the shortcomings of the MOC caused by using a truncated series expansion for the particle displacements, and neglecting plastic flow and nonadiabatic effects are discussed.

Clements, B. E.; Johnson, J. N.; Hixson, R. S.

1996-12-01

118

Oxygen Compatibility Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

The development of polymer composite liquid oxygen LO2 tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 25%-40% reduction in weight that composite materials could provide over current aluminum technology. Although a composite LO2 tank makes these weight savings feasible, composite materials have not historically been viewed as "LO2 compatible." To be considered LO2 compatible, materials must be selected that will resist any type of detrimental, combustible reaction when exposed to usage environments. This is traditionally evaluated using a standard set of tests. However, materials that do not pass the standard tests can be shown to be safe for a particular application. This paper documents the approach and results of a joint NASA/Lockheed Martin program to select and verify LO2 compatible composite materials for liquid oxygen fuel tanks. The test approach developed included tests such as mechanical impact, particle impact, puncture, electrostatic discharge, friction, and pyrotechnic shock. These tests showed that composite liquid oxygen tanks are indeed feasible for future launch vehicles.

Graf, Neil A.; Hudgins, Richard J.; McBain, Michael

2000-01-01

119

3-D textile reinforcements in composite materials  

SciTech Connect

Laminated composite materials have been used in structural applications since the 1960s. However, their high cost and inability to accommodate fibers in the laminate`s thickness direction greatly reduce their damage tolerance and impact resistance. The second generation of materials--3-D textile reinforced composites--offers significant cost reduction, and by incorporating reinforcement in the thickness direction, dramatically increases damage tolerance and impact resistance. However, methods for predicting mechanical properties of 3-D textile reinforced composite materials tend to be more complex. These materials also have disadvantages--particularly in regard to crimps in the yarns--that require more research. Textile preforms, micro- and macromechanical modeling, manufacturing processes, and characterization all need further development. As researchers overcome these problems, this new generation of composites will emerge as a highly competitive family of materials. This book provides a state-of-the-art account of this promising technology. In it, top experts describe the manufacturing processes, highlight the advantages, identify the main applications, analyze methods for predicting mechanical properties, and detail various reinforcement strategies, including grid structure, knitted fabric composites, and the braiding technique. Armed with the information in this book, readers will be prepared to better exploit the advantages of 3-D textile reinforced composites, overcome its disadvantages, and contribute to the further development of the technology.

Miravete, A. [Univ. of Zaragoza (Spain)

1999-11-01

120

Introduction to naturally occurring radioactive material.  

National Technical Information Service (NTIS)

Naturally occurring radioactive material (NORM) is everywhere; we are exposed to it every day. It is found in our bodies, the food we eat, the places where we live and work, and in products we use. We are also bathed in a sea of natural radiation coming f...

P. Egidi

1997-01-01

121

Introduction to naturally occurring radioactive material  

Microsoft Academic Search

Naturally occurring radioactive material (NORM) is everywhere; we are exposed to it every day. It is found in our bodies, the food we eat, the places where we live and work, and in products we use. We are also bathed in a sea of natural radiation coming from the sun and deep space. Living systems have adapted to these levels

Egidi

1997-01-01

122

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.  

SciTech Connect

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70 degC. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 degC lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

2012-02-01

123

New types of reinforced composite materials  

Microsoft Academic Search

The physical properties of solids determine their usefulness as structural materials. Metals have some disadvantageous characteristics which reduce their effectiveness in critical engineering applications. These limitations can be overcome by the use of certain types of fibrous reinforced composites which have become available over the last few years. However, these materials in turn have their own inherent limitations, particularly in

J. G. Morley

1976-01-01

124

Pressure variation assisted fiber extraction and development of high performance natural fiber composites and nanocomposites  

Microsoft Academic Search

It is believed, that due to the large surface areas provided by the nano scale materials, various composite properties could be enhanced when such particles are incorporated into a polymer matrix. There is also a trend of utilizing natural resources or reusing and recycling materials that are already available for the fabrication of the new composite materials. Cellulose is the

Gediminas Markevicius

2010-01-01

125

Energy absorption of composite material and structure  

NASA Technical Reports Server (NTRS)

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Farley, Gary L.

1987-01-01

126

Damping in aerospace composite materials  

NASA Astrophysics Data System (ADS)

Experimental results are presented on specimens of carbon and Kevlar fibers in epoxy resin, materials used in many aerospace structures (control surfaces and wings in aircraft, large antennas in spacecraft, etc.). Some experimental methods of estimating damping ratios are first reviewed, either in the time domain or in the frequency domain. Some damping factor estimates from experimental tests are then shown; in order to evaluate the effects of the aerospace environment, damping factors have been obtained in a typical range of temperature, namely between +120 C and -120 C, and in the pressure range from room pressure to 10 exp -6 torr. Finally, a theoretical approach for predicting the bounds of the damping coefficients is shown, and prediction data are compared with experimental results.

Agneni, A.; Balis Crema, L.; Castellani, A.

127

Cell Attachment to Hydrogel-Electrospun Fiber Mat Composite Materials  

PubMed Central

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials.

Han, Ning; Johnson, Jed K.; Bradley, Patrick A.; Parikh, Kunal S.; Lannutti, John J.; Winter, Jessica O.

2012-01-01

128

Cell attachment to hydrogel-electrospun fiber mat composite materials.  

PubMed

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials. PMID:24955629

Han, Ning; Johnson, Jed K; Bradley, Patrick A; Parikh, Kunal S; Lannutti, John J; Winter, Jessica O

2012-01-01

129

ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS  

SciTech Connect

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for {sup 236}U/{sup 235}U in SRM950a was determined to be (8.48 {+-} 2.63) x 10{sup -6}, whereas {sup 236}U was not detected in CRM112a. They are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the {sup 238}U/{sup 235}U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

2009-09-03

130

Composite Materials for Wind Power Turbine Blades  

NASA Astrophysics Data System (ADS)

Renewable energy resources, of which wind energy is prominent, are part of the solution to the global energy problem. Wind turbine and the rotorblade concepts are reviewed, and loadings by wind and gravity as important factors for the fatigue performance of the materials are considered. Wood and composites are discussed as candidates for rotorblades. The fibers and matrices for composites are described, and their high stiffness, low density, and good fatigue performance are emphasized. Manufacturing technologies for composites are presented and evaluated with respect to advantages, problems, and industrial potential. The important technologies of today are prepreg (pre-impregnated) technology and resin infusion technology. The mechanical properties of fiber composite materials are discussed, with a focus on fatigue performance. Damage and materials degradation during fatigue are described. Testing procedures for documentation of properties are reviewed, and fatigue loading histories are discussed, together with methods for data handling and statistical analysis of (large) amounts of test data. Future challenges for materials in the field of wind turbines are presented, with a focus on thermoplastic composites, new structural materials concepts, new structural design aspects, structural health monitoring, and the coming trends and markets for wind energy.

Brndsted, Povl; Lilholt, Hans; Lystrup, Aage

2005-08-01

131

Mechanical property evaluation of natural fiber coir composite  

SciTech Connect

The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. Past studies show that only artificial fibers such as glass, carbon etc., have been used in fiber-reinforced plastics. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. In the present work, coir composites are developed and their mechanical properties are evaluated. Scanning electron micrographs obtained from fractured surfaces were used for a qualitative evaluation of the interfacial properties of coir/epoxy and compared with glass fiber/epoxy. These results indicate that coir can be used as a potential reinforcing material for making low load bearing thermoplastic composites.

Harish, S. [Department of Mechanical and Aerospace Engineering, Arizona State University (United States); Michael, D. Peter [Department of Mechanical Engineering, College of Engineering, Guindy (India); Bensely, A. [Department of Mechanical Engineering, College of Engineering, Guindy (India)], E-mail: benzlee5@yahoo.com; Lal, D. Mohan [Department of Mechanical Engineering, College of Engineering, Guindy (India); Rajadurai, A. [Department of Production Engineering, Madras Institute of Technology (India)

2009-01-15

132

Tensile failure criteria for fiber composite materials  

NASA Technical Reports Server (NTRS)

The analysis provides insight into the failure mechanics of these materials and defines criteria which serve as tools for preliminary design material selection and for material reliability assessment. The model incorporates both dispersed and propagation type failures and includes the influence of material heterogeneity. The important effects of localized matrix damage and post-failure matrix shear stress transfer are included in the treatment. The model is used to evaluate the influence of key parameters on the failure of several commonly used fiber-matrix systems. Analyses of three possible failure modes were developed. These modes are the fiber break propagation mode, the cumulative group fracture mode, and the weakest link mode. Application of the new model to composite material systems has indicated several results which require attention in the development of reliable structural composites. Prominent among these are the size effect and the influence of fiber strength variability.

Rosen, B. W.; Zweben, C. H.

1972-01-01

133

Indentation cracking of composite matrix materials.  

PubMed

Composite restorative materials wear by a fatigue mechanism in the occlusal contact area. Here, tooth cusps and food debris cyclically indent the restoration. Modeling this phenomenon requires an understanding of material response to indentation. The question in this study was whether material response depends on indenter size and geometry, and also, whether polymers used in restorative materials should be considered elastic and brittle, or plastic and ductile for modeling purposes. Three resins used as matrices in proprietary restorative composites were the experimental materials. To ascertain the influence of glass transition temperature, liquid sorption, and small amounts of filler on indentation response, we prepared materials with various degrees of cure; some samples were soaked in a 50/50 water/ethanol solution, and 3 vol% silica was added in some cases. Indentation experiments revealed that no cracking occurred in any material after indentation by Vickers pyramid or spherical indenters with diameters equal to or smaller than 0.254 mm. Larger spherical indenters induced subsurface median and surface radial and/or ring cracks. Critical loads causing subsurface cracks were measured. Indentation with suitably large spherical indenters provoked an elastoplastic response in polymers, and degree of cure and Tg had less influence on critical load than soaking in solution. Crack morphology was correlated with yield strain. Commonly held assumptions regarding the brittle elastic behavior of composite matrix materials may be incorrect. PMID:8083442

Baran, G; Shin, W; Abbas, A; Wunder, S

1994-08-01

134

Properties of five toughened matrix composite materials  

NASA Technical Reports Server (NTRS)

The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and unnotched tension and compression properties of quasi-isotropic laminates, and compression-after-impact strengths of five carbon fiber/toughened matrix composites, IM7/E7T1-2, IM7/X1845, G40-800X/5255-3, IM7/5255-3, and IM7/5260 have been evaluated. The compression-after-impact (CAI) strengths were determined primarily by impacting quasi-isotropic laminates with the NASA Langley air gun. A few CAI tests were also made with a drop-weight impactor. For a given impact energy, compression after impact strengths were determined to be dependent on impactor velocity. Properties and strengths for the five materials tested are compared with NASA data on other toughened matrix materials (IM7/8551-7, IM6/1808I, IM7/F655, and T800/F3900). This investigation found that all five materials were stronger and more impact damage tolerant than more brittle carbon/epoxy composite materials currently used in aircraft structures.

Cano, Roberto J.; Dow, Marvin B.

1992-01-01

135

Damping Experiment of Spinning Composite Plates with Embedded Viscoelastic Material  

NASA Technical Reports Server (NTRS)

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration reduction can be achieved by adding damping to metal and composite blade-disk systems. This experiment was done to investigate the use of integral viscoelastic damping treatments to reduce vibration of rotating composite fan blades. It is part of a joint research effort with NASA LeRC and the University of California, San Diego (UCSD). Previous vibration bench test results obtained at UCSD show that plates with embedded viscoelastic material had over ten times greater damping than similar untreated plates; and this was without a noticeable change in blade stiffness. The objectives of this experiment, were to verify the structural integrity of composite plates with viscoelastic material embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Mehmed, Oral; Kosmatka, John B.

1997-01-01

136

Elementary damping properties in braided composite materials  

Microsoft Academic Search

This paper investigates the damping level trends of three-dimensionally braided composites as a function of matrix material, fiber-matrix interface, fiber braid angle, fiber volume, and axial fiber tow size. With knowledge of such trends, designers may increase the structural damping in a 3-D braided composite component, thereby reducing component vibration, shock response, and fatigue. The logarithmic decrements of the fundamental

Bernard L. Dion; Robert Sadler; Larry Silverberg

1994-01-01

137

Impact testing of textile composite materials  

NASA Technical Reports Server (NTRS)

The objectives of this report were to evaluate the impact damage resistance and damage tolerance of a variety of textile composite materials. Static indentation and impact tests were performed on the stitched and unstitched uniweave composites constructed from AS4/3501-6 Carbon/Epoxy with a fiberglass yarn woven in to hold the fibers together while being stitched. Compression and tension were measured after the tests to determine the damage resistance, residual strength and the damage tolerance of the specimens.

Portanova, Marc

1995-01-01

138

Discrimination of Naturally Occurring Radioactive Material in Plastic Scintillator Material  

SciTech Connect

Plastic scintillator material is used in many applications for the detection of gamma-rays from radioactive material, primarily due to the sensitivity per unit cost compared to other detection materials. However, the resolution and lack of full-energy peaks in the plastic scintillator material prohibits detailed spectroscopy. Therefore, other materials such as doped sodium iodide are used for spectroscopic applications. The limited spectroscopic information can however be exploited in plastic scintillator materials to provide some discrimination. The discrimination between man-made and naturally occurring sources would be useful in reducing alarm screening for radiation detection applications which target man-made sources. The results of applying the limited energy information from plastic scintillator material for radiation portal monitors are discussed.

Ely, James H.; Kouzes, Richard T.; Geelhood, Bruce D.; Schweppe, John E.; Warner, Ray A.

2003-08-19

139

Frequency Response Engineering of Magnetic Composite Materials  

Microsoft Academic Search

\\u000a Ferromagnetic metals have attractive microwave magnetic properties, but because of their conductivity, they can not be used\\u000a under bulk form, and have to be made into composite materials. Ferromagnetic-based composites may be categorized into C2D,\\u000a C1D and COD depending on the number of macroscopic Conducting Dimensions they have. C2D and C1D composites are made from thin\\u000a films and thin wires

Olivier Acher; CEA Le Ripault

140

Computational modeling of composite material fires.  

SciTech Connect

Composite materials behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite materials on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite material response in fires including the decomposition of the composite and the interaction with a fire. To adequately model composite material in a fire, two physical model development tasks are necessary; first, the decomposition model for the composite material and second, the interaction with a fire. A porous media approach for the decomposition model including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the porous solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction model is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite material subject to a radiant heat flux boundary condition is examined to study the propagation of decomposition fronts of the epoxy and carbon fiber and their dependence on the ambient conditions such as oxygen concentration, surface flow velocity, and radiant heat flux. In addition to the computational effort, small scaled experimental efforts to attain adequate data used to validate model predictions is ongoing. The goal of this paper is to demonstrate the progress of the capability for a typical composite material and emphasize the path forward.

Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.

2010-10-01

141

Material properties of living soft tissue composites.  

PubMed

Collagen sponges seeded with fibroblasts have been used as a soft tissue substitute in wound healing applications. This biomaterial is a good in vitro analog of a connective tissue. Therefore, analysis of the properties of this material may be useful for theoretically modeling soft tissues. Stress-strain curves for such cell-seeded collagen sponges were measured to determine composite stiffness and ultimate tensile strength. Theoretical modeling was done by defining a particle-reinforced matrix using the composite sphere model. A system of uniaxially oriented fibers was then introduced to this equivalent homogeneous media and material properties were determined using the composite cylinder model. Geometric averaging was performed to yield the stiffness and Poissons' ratio for a composite with randomly oriented fibers. Inputs to the model were constituent material properties, cell volume fraction, and fiber volume fraction. From theoretical results, material properties of soft tissues and their substitutes depend on fiber mechanical properties and volume fraction and not cellular mechanical properties and volume fraction. Therefore, the increase in experimentally observed composite stiffness with increased cell number was due to deposition of newly synthesized stiffer collagen fibers, and not due to the physical presence of cells themselves. PMID:3235466

Jain, M K; Chernomorsky, A; Silver, F H; Berg, R A

1988-12-01

142

Composite materials and method of making  

DOEpatents

A method of depositing noble metals on a metal hexaboride support. The hexaboride support is sufficiently electropositive to allow noble metals to deposit spontaneously from solutions containing ionic species of such metals onto the support. The method permits the deposition of metallic films of controlled thickness and particle size at room temperature without using separate reducing agents. Composite materials comprising noble metal films deposited on such metal hexaborides are also described. Such composite materials may be used as catalysts, thermionic emitters, electrical contacts, electrodes, adhesion layers, and optical coatings.

Uribe, Francisco A. (Los Alamos, NM) [Los Alamos, NM; Wilson, Mahlon S. (Los Alamos, NM) [Los Alamos, NM; Garzon, Fernando H. (Santa Fe, NM) [Santa Fe, NM

2009-09-15

143

Thermal expansion properties of composite materials  

NASA Technical Reports Server (NTRS)

Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications.

Johnson, R. R.; Kural, M. H.; Mackey, G. B.

1981-01-01

144

Ground exposure of composite materials for helicopters  

NASA Technical Reports Server (NTRS)

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

Baker, D. J.

1984-01-01

145

Mimicry of natural material designs and processes  

SciTech Connect

Biological structural materials, although composed of unremarkable substances synthesized at low temperatures, often exhibit superior mechanical properties. In particular, the quality in which nearly all biologically derived materials excel is toughness. The advantageous mechanical properties are attributable to the hierarchical, composite, structural arrangements common to biological systems. Materials scientists and engineers have increasingly recognized that biological designs or processing approaches applied to man-made materials (biomimesis) may offer improvements in performance over conventional designs and fabrication methods. In this survey, the structures and processing routes of marine shells, avian eggshells, wood, bone, and insect cuticle are briefly reviewed, and biomimesis research inspired by these materials is discussed. In addition, this paper describes and summarizes the applications of biomineralization, self-assembly, and templating with proteins to the fabrication of thin ceramic films and nanostructure devices.

Bond, G.M. [New Mexico Inst. of Mining and Technology, Socorro, NM (United States); Richman, R.H. [Daedalus Associates, Inc., Mountain View, CA (United States); McNaughton, W.P. [Cornice Engineering, Durango, CO (United States)

1995-06-01

146

Delamination from surface cracks in composite materials  

Microsoft Academic Search

Some aspects of splitting and delamination of composite materials from surface flaws are discussed. The system modelled is\\u000a one of an elastically homogeneous material containing aligned interfaces. This simplified model, although missing some of\\u000a the details that would be associated with elastic inhomogeneity, does permit a discussion of some of the factors that govern\\u000a this type of delamination.

M. D. Thouless; H. C. Cao; P. A. Mataga

1989-01-01

147

Synthesizing Smart Polymeric and Composite Materials  

NASA Astrophysics Data System (ADS)

Smart materials have been widely investigated to explore new functionalities unavailable to traditional materials or to mimic the multifunctionality of biological systems. Synthetic polymers are particularly attractive as they already possess some of the attributes required for smart materials, and there are vast room to further enhance the existing properties or impart new properties by polymer synthesis or composite formulation. In this work, three types of smart polymer and composites have been investigated with important new applications: (1) healable polymer composites for structural application and healable composite conductor for electronic device application; (2) conducting polymer polypyrrole actuator for implantable medical device application; and (3) ferroelectric polymer and ceramic nanoparticles composites for electrocaloric effect based solid state refrigeration application. These application entail highly challenging materials innovation, and my work has led to significant progress in all three areas. For the healable polymer composites, well known intrinsically healable polymer 2MEP4F (a Diels-Alder crosslinked polymer formed from a monomer with four furan groups and another monomer with two maleimide groups) was first chosen as the matrix reinforced with fiber. Glass fibers were successfully functionalized with maleimide functional groups on their surface. Composites from functionalized glass fibers and 2MEP4F healable polymer were made to compare with composites made from commercial carbon fibers and 2MEP4F polymer. Dramatically improved short beam shear strength was obtained from composite of functionalized glass fibers and 2MEP4F polymer. The high cost of 2MEP4F polymer can potentially limit the large-scale application of the developed healable composite, we further developed a new healable polymer with much lower cost. This new polymer was formed through the Diels-Alder crosslinking of poly(furfuryl alcohol) (PFA) and 1,1'-(Methylenedi-4,1-phenylene)bismaleimide (MDPB). It showed the same healing ability as 2MEP4F while all starting materials are cheaper and commercially available. To further improve the mechanical strength of the PFA-MDPB healable polymer, epoxy as a strengthening component was mixed with PFA-MDPB healable polymer. The PFA, MDPB and epoxy composite polymers were further reinforced by carbon fiber as done with 2MEP4F matrix and the final composites were proved to have higher short beam shear strength than 2MEP4F while exhibiting a similar healing efficiency. Healable polymer MDPB (a two maleimide groups monomer) -- FGEEDR (a four furan groups monomer) was also designed and synthesized for transparent healable polymer. The MDPB-FGEEDR healable polymer was composited with silver nanowires (AgNWs) to afford healable transparent composite conductor. Razer blade cuts in the composite conductor could heal upon heating to recover the mechanical strength and electrical conductivity of the composite. The healing could be repeated for multiple times on the same cut location. The healing process was as fast as 3 minutes for conductivity to recover 97% of the original value. For electroactive polymer polypyrrole, the fast volume change upon electrical field change due to electrochemical oxidization or reduction was studied for actuation targeting toward a robotic application. The flexibility of polypyrrole was improved via copolymerization with pyrrole derivatives. Actuator devices are fabricated that more suitable for implantable medical device application than pyrrole homopolymer. The change of dipole re-orientation and thus dielectric constant of ferroelectric polymers and ceramics upon electrical field may be exploited for electrocaloric effect (ECE) and solid state refrigeration. For ferroelectric ceramics, we synthesized a series of Ba1-xSrxTiO3 nanoparticles with diameter ranging from 8-12 nm and characterized their dielectric and ferroelectric properties through hysteresis measurement. It was found that 8 nm BaTiO3 nanocrystals are stable at cubic crystal structure without ferroelectric

Gong, Chaokun

148

Composite materials for rail transit systems  

NASA Technical Reports Server (NTRS)

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

149

Composite materials for the extravehicular mobility unit  

NASA Technical Reports Server (NTRS)

The extravehicular mobility unit (EMU), commonly known as the astronaut space suit assembly (SSA) and primary life support system (PLSS), has evolved through the years to incorporate new and innovative materials in order to meet the demands of the space environment. The space shuttle program which is seeing an increasing level of extravehicular activity (EVA), also called space walks, along with interest in an EMU for Lunar-Mars missions means even more demanding conditions are being placed on the suit and PLSS. The project for this NASA-ASEE Summer Program was to investigate new materials for these applications. The focus was to emphasize the use of composite materials for every component of the EMU to enhance the properties while reducing the total weight of the EMU. To accomplish this, development of new materials called fullerene reinforced materials (FRM's) was initiated. Fullerenes are carbon molecules which when added to a material significantly reduce the weight of that material. The Faculty Fellow worked directly on the development of the fullerene reinforced materials. A chamber for fullerene production was designed and assembled and first generation samples were processed. He also supervised with the JSC Colleague, a study of composite materials for the EMU conducted by the student participant in the NASA-ASEE Program, Hector Tello a Rice University graduate student, and by a NASA Aerospace Technologist (Materials Engineer) Evelyne Orndoff, in the Systems Engineering Analysis Office (EC7), also a Rice University graduate student. Hector Tello conducted a study on beryllium and Be alloys and initiated a study of carbon and glass reinforced composites for space applications. Evelyne Orndoff compiled an inventory of the materials on the SSA. Ms. Orndoff also reviewed SSA material requirements and cited aspects of the SSA design where composite materials might be further considered. Hector Tello spent part of his time investigating the solar radiation sensitivity of anodic coatings. This project was directed toward the effects of ultra-violet radiation on high emissivity anodic coatings. The work of both Evelyne Orndoff and Hector Tello is of interest to the Engineering Directorate at NASA/JSC and is also directed toward their research as Rice University graduate students.

Barrera, Enrique V.; Tello, Hector M.

1992-01-01

150

Thermoplastic Composite Materials for Aerospace Applications  

NASA Astrophysics Data System (ADS)

Mechanical and thermo-physical properties of composites materials with thermoplastic matrix (PEEK/IM7, TPI/IM7 and PPS/IM7) used for aerospace applications have been analyzed as function of two different process techniques: compression molding and fiber placement process ``hot gas assisted.''

Casula, G.; Lenzi, F.; Vitiello, C.

2008-08-01

151

COMPOSITE MATERIALS FOR INNOVATIVE WIND TURBINE BLADES  

Microsoft Academic Search

The Wind Energy Technology Department at Sandia National Laboratories (SNL) focuses on producing innovations in wind turbine blade technology to enable the development of longer blades that are lighter, more structurally and aerodynamically efficient, and impart reduced loads to the system. A large part of the effort is to characterize the properties of relevant composite materials built with typical manufacturing

Thomas D. Ashwill; Joshua A. Paquette

152

Energy absorbing hybrid nano-composite materials  

Microsoft Academic Search

Base Epon 862 resin was enhanced with two types of fillers, graphitized carbon nanofiber (CNF) and silicon dioxide (SiO2) particles. The effect of both filler type and filler loading were investigated with respect to the energy absorbing capacity as well as the thermal stability of the hybrid composite material, measured in terms of the coefficient of thermal expansion (CTE). As

Jae-Soon Jang; Joshua Varischetti; Gyo Woo Lee; Jonghwan Suhr

2009-01-01

153

Thermal diffusivity of composite restorative materials.  

PubMed

The substantial increases in the filler volume fraction of the current generation of composite resins, and the incorporation of radiopacifying heavy elements in many of these fillers, constitute significant changes which may affect thermal transport properties. Thermal diffusivity has been determined for 21 of these composite materials recommended for anterior and posterior applications. For radiopaque hybrid and for microfine composites, there was, however, only a gradual trend to increased thermal diffusivity with increasing volume fraction of inorganic filler. The diffusivity values were not greatly in excess of the level observed for dentin. Nevertheless, a small group of materials, incorporating substantial amounts of quartz or silicon nitride filler particles, exhibited high rates of thermal diffusion, up to three times the level exhibited by dentin. PMID:3040822

Watts, D C; McAndrew, R; Lloyd, C H

1987-10-01

154

Accelerated Aging of Polymer Composite Bridge Materials  

SciTech Connect

Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

Carlson, Nancy Margaret; Blackwood, Larry Gene; Torres, Lucinda Laine; Rodriguez, Julio Gallardo; Yoder, Timothy Scott

1999-03-01

155

Accelerated aging of polymer composite bridge materials  

NASA Astrophysics Data System (ADS)

Accelerated aging research on samples of composite materials and candidate UV protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory. Durability results and sensor data form test with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards and acceptance criteria for PMC bridges for use in the transportation infrastructure.

Carlson, Nancy M.; Blackwood, Larry G.; Torres, Lucinda L.; Rodriguez, Julio G.; Yoder, Timothy S.

1999-05-01

156

Mishap risk control for advanced aerospace/composite materials  

NASA Technical Reports Server (NTRS)

Although advanced aerospace materials and advanced composites provide outstanding performance, they also present several unique post-mishap environmental, safety, and health concerns. The purpose of this paper is to provide information on some of the unique hazards and concerns associated with these materials when damaged by fire, explosion, or high-energy impact. Additionally, recommended procedures and precautions are addressed as they pertain to all phases of a composite aircraft mishap response, including fire-fighting, investigation, recovery, clean-up, and guidelines are general in nature and not application-specific. The goal of this project is to provide factual and realistic information which can be used to develop consistent and effective procedures and policies to minimize the potential environmental, safety, and health impacts of a composite aircraft mishap response effort.

Olson, John M.

1994-01-01

157

Conductor-polymer composite electrode materials  

DOEpatents

A conductive composite material useful as an electrode, comprises a conductor and an organic polymer which is reversibly electrochemically dopable to change its electrical conductivity. Said polymer continuously surrounds the conductor in intimate electrical contact therewith and is prepared by electrochemical growth on said conductor or by reaction of its corresponding monomer(s) on said conductor which has been pre-impregnated or pre-coated with an activator for said polymerization. Amount of the conductor is sufficient to render the resultant composite electrically conductive even when the polymer is in an undoped insulating state.

Ginley, D.S.; Kurtz, S.R.; Smyrl, W.H.; Zeigler, J.M.

1984-06-13

158

Mechanical Spectroscopy of Nanostructured Composite Materials  

NASA Astrophysics Data System (ADS)

The thermo-mechanical behavior of different nano-structured composite materials, which were processed within the SAPHIR European Integrated Project, has been characterized by mechanical spectroscopy. The obtained results show clearly that creep resistance of fine grain ceramics such as zirconia can be improved by carbon nano-tube (CNT) reinforcements. On the other hand the elastic modulus and the damping capacity of aluminum matrix composites were increased by SiC nano-particle additions. It has also been observed that CNT additions are responsible for a better thermal stability of polymer such as ABS (Acrylonitrile-Butadiene-Styrene) used in automotive industry.

Mari, Daniele; Schaller, Robert; Mazaheri, Mehdi

2011-07-01

159

Damping Experiment of Spinning Composite Plates With Embedded Viscoelastic Material  

NASA Technical Reports Server (NTRS)

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration can be reduced by adding damping to metal and composite blade-disk systems. As part of a joint research effort of the NASA Lewis Research Center and the University of California, San Diego, the use of integral viscoelastic damping treatment to reduce the vibration of rotating composite fan blades was investigated. The objectives of this experiment were to verify the structural integrity of composite plates with viscoelastic material patches embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Mehmed, Oral

1998-01-01

160

Natural radioactivity of granites used as building materials.  

PubMed

Sixteen kinds of different granites, used as building materials, imported to Greece mainly from Spain and Brazil, were sampled and their natural radioactivity was measured by gamma-ray spectrometry. The activity concentrations of (238)U, (226)Ra, (232)Th and (40)K of granites are presented and compared to those of other building materials as well as other granite types used all over the world. In order to assess the radiological impact from the granites investigated, the absorbed and the effective doses were determined. Although the annual effective dose is higher than the limit of 1mSvy(-1) for some studied granites, they could be used safely as building materials, considering that their contribution in most of the house constructions is very low. An attempt to correlate the relatively high level of natural radioactivity, shown by some of the granites, with their constituent radioactive minerals and their chemical composition, was also made. PMID:16713662

Pavlidou, S; Koroneos, A; Papastefanou, C; Christofides, G; Stoulos, S; Vavelides, M

2006-01-01

161

Compression Testing of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

The applicability of existing test methods, which were developed primarily for laminates made of unidirectional prepreg tape, to textile composites is an area of concern. The issue is whether the values measured for the 2-D and 3-D braided, woven, stitched, and knit materials are accurate representations of the true material response. This report provides a review of efforts to establish a compression test method for textile reinforced composite materials. Experimental data have been gathered from several sources and evaluated to assess the effectiveness of a variety of test methods. The effectiveness of the individual test methods to measure the material's modulus and strength is determined. Data are presented for 2-D triaxial braided, 3-D woven, and stitched graphite/epoxy material. However, the determination of a recommended test method and specimen dimensions is based, primarily, on experimental results obtained by the Boeing Defense and Space Group for 2-D triaxially braided materials. They evaluated seven test methods: NASA Short Block, Modified IITRI, Boeing Open Hole Compression, Zabora Compression, Boeing Compression after Impact, NASA ST-4, and a Sandwich Column Test.

Masters, John E.

1996-01-01

162

Filament-wound composite vessels material technology  

NASA Technical Reports Server (NTRS)

Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

Lark, R. F.

1973-01-01

163

Multiaxial analysis of dental composite materials.  

PubMed

Dental composites are subjected to extreme chemical and mechanical conditions in the oral environment, contributing to the degradation and ultimate failure of the material in vivo. The objective of this study is to validate an alternative method of mechanically loading dental composite materials. Confined compression testing more closely represents the complex loading that dental restorations experience in the oral cavity. Dental composites, a nanofilled and a hybrid microfilled, were prepared as cylindrical specimens, light-cured in ring molds of 6061 aluminum, with the ends polished to ensure parallel surfaces. The samples were subjected to confined compression loading to 3, 6, 9, 12, and 15% axial strain. Upon loading, the ring constrains radial expansion of the specimen, generating confinement stresses. A strain gage placed on the outer wall of the aluminum confining ring records hoop strain. Assuming plane stress conditions, the confining stress (sigma(c)) can be calculated at the sample/ring interface. Following mechanical loading, tomographic data was generated using a high-resolution microtomography system developed at beamline 2-BM of the Advanced Photon Source at Argonne National Laboratory. Extraction of the crack and void surfaces present in the material bulk is numerically represented as crack edge/volume (CE/V), and calculated as a fraction of total specimen volume. Initial results indicate that as the strain level increases the CE/V increases. Analysis of the composite specimens under different mechanical loads suggests that microtomography is a useful tool for three-dimensional evaluation of dental composite fracture surfaces. PMID:18506811

Kotche, Miiri; Drummond, James L; Sun, Kang; Vural, Murat; DeCarlo, Francesco

2009-02-01

164

Development and characterization of optical composite materials  

NASA Astrophysics Data System (ADS)

This thesis describes the development of a new class of optical gain media: optical composites. This work originated in a research project to develop new tunable laser materials based on crystals containing the tetravalent chromium ion located in oxygen tetrahedra. This project encompassed co-doping the Cr:forsterite (Cr:Mg2SiO4) crystal lattice with additional impurities to distort the environment of the Cr4+ ions, as well as investigating alternate host crystals featuring oxygen tetrahedra. This project lead to the identification of Cr:diopside (Cr:CaMgSi2O6) as a promising candidate for a tunable laser material based on the Cr4+ ion. Since diopside is difficult to grow into single crystal form, it is unsuitable for use as a conventional solid- state laser gain medium, which requires a sizable single crystal. This led to the development of the optical composite scheme, in which tiny nanocrystals of the gain medium are embedded within a host matrix, thereby eliminating the requirement of obtaining a large single crystal of the gain medium. Scattering losses and small particle effects are considered, as these issues arise with the use of nanoparticle-containing composites. In addition, the spectroscopy of Cr:diopside is examined to identify the charge states and energy levels involved in absorption and emission processes in this material. Finally, the fabrication of waveguide amplifiers out of optical composites is discussed. Amplification results for waveguide amplifiers of both Cr:forsterite and Cr:diopside composites are presented.

Barber, Duane Byron

1997-11-01

165

Metal Matrix Composite Materials for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Metal matrix composites (MMC) are attractive materials for aerospace applications because of their high specific strength, high specific stiffness, and lower thermal expansion coefficient. They are affordable since complex parts can be produced by low cost casting process. As a result there are many commercial and Department of Defense applications of MMCs today. This seminar will give an overview of MMCs and their state-of-the-art technology assessment. Topics to be covered are types of MMCs, fabrication methods, product forms, applications, and material selection issues for design and manufacture. Some examples of current and future aerospace applications will also be presented and discussed.

Bhat, Biliyar N.; Jones, C. S. (Technical Monitor)

2001-01-01

166

Mechanical Spectroscopy of Nanostructured Composite Materials  

Microsoft Academic Search

The thermo-mechanical behavior of different nano-structured composite materials, which were processed within the SAPHIR European Integrated Project, has been characterized by mechanical spectroscopy. The obtained results show clearly that creep resistance of fine grain ceramics such as zirconia can be improved by carbon nano-tube (CNT) reinforcements. On the other hand the elastic modulus and the damping capacity of aluminum matrix

Daniele Mari; Robert Schaller; Mehdi Mazaheri

2011-01-01

167

Stresses around fasteners in composite materials  

NASA Astrophysics Data System (ADS)

Stress distributions around fasteners in composite materials were experimentally and theoretically studied. The fasteners were cheesehead and countersunk bolts. It was found that samples fastened with countersunk bolts tended to fatigue more rapidly than specimens with cheesehead bolts. Fewer fatigue cycles were needed for damage to initiate in plates with countersunk bolts, and higher direct stress and shear stress values are predicted to occur in plates with countersunk bolts. The principal failure mechanism was delamination, probably due to high direct and shear stresses.

Benchekchou, B.; White, R. G.

1993-04-01

168

Test Plan for Composite Hydrogen Getter Materials  

Microsoft Academic Search

The intent of this test plan is to provide details of the Savannah River Technology Center (SRTC) effort to evaluate composite getter materials for eventual use in expanding the wattage limits for transportation of contact-handled transuranic waste (CH-TRU). This effort is funded by the Mixed Waste Focus Area (MWFA) under Technical Task Plan (TTP) SR-1-9-MW-45 and is the result of

2000-01-01

169

Epoxide composite materials with carbon nanotubes  

NASA Astrophysics Data System (ADS)

Methods of formation and physical properties of epoxide composite materials reinforced with carbon nanotubes are considered. An analogy is made between the relaxation properties of carbon nanotubes and macromolecules. The concentration dependences of the electrical conductivity of the epoxy polymers filled with single-walled and multi-walled carbon nanotubes are discussed. Modern views on the mechanism of reinforcement of polymers with nanotubes are outlined. The bibliography includes 143 references.

Irzhak, Vadim I.

2011-08-01

170

Development and characterization of optical composite materials  

Microsoft Academic Search

This thesis describes the development of a new class of optical gain media: optical composites. This work originated in a research project to develop new tunable laser materials based on crystals containing the tetravalent chromium ion located in oxygen tetrahedra. This project encompassed co-doping the Cr:forsterite (Cr:Mg2SiO4) crystal lattice with additional impurities to distort the environment of the Cr4+ ions,

Duane Byron Barber

1997-01-01

171

On the effective conductivity of composite materials  

Microsoft Academic Search

A composite conductive material, which consists of fibers of a high conductivity in a matrix of low conductivity, is discussed.\\u000a The effective conductivity of the system considered is calculated in Clausius-Mossotti approximation. Obtained relationships\\u000a can be used to calculate the conductivity of a matrix, using experimentally measured parameters. Electric fields in the matrix\\u000a and the inclusions are calculated. It is

Yu. V. Kornyushin

2010-01-01

172

Mechanics Methodology for Textile Preform Composite Materials  

NASA Technical Reports Server (NTRS)

NASA and its contractors have completed a program to develop a basic mechanics underpinning for textile composites. Three major deliverables were produced by the program: 1. A set of test methods for measuring material properties and design allowables; 2. Mechanics models to predict the effects of the fiber preform architecture and constituent properties on engineering moduli, strength, damage resistance, and fatigue life; and 3. An electronic data base of coupon type test data. This report describes these three deliverables.

Poe, Clarence C., Jr.

1996-01-01

173

Alkali metal protective garment and composite material  

DOEpatents

A protective garment and composite material providing satisfactory heat resistance and physical protection for articles and personnel exposed to hot molten alkali metals, such as sodium. Physical protection is provided by a continuous layer of nickel foil. Heat resistance is provided by an underlying backing layer of thermal insulation. Overlying outer layers of fireproof woven ceramic fibers are used to protect the foil during storage and handling.

Ballif, III, John L. (Salt Lake City, UT); Yuan, Wei W. (Seattle, WA)

1980-01-01

174

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

Composite materials are light, strong, corrosion-resistant composites of two or more materials used commonly in manufacturing. This recent report is from the Australian Academy of Science with support from The Cooperative Research Centre for Advanced Composite Structures, Ltd. and the Commonwealth Department of Industry, Science and Resources. It gives information on the history, manufacturing techniques, and efficiency of composite materials. A glossary, reference list, and links to educational sites as well as other composite materials sites are also featured.

2000-01-01

175

The Nature of Genetic Material Online Module  

NSDL National Science Digital Library

The Nature of Genetic Material, a new resource from Baylor College of Medicineâs comprehensive website, BioEd Online, is one module of a three-part, interactive Web-based course called Genes, Health and Society. [The course, which explores the rapidly evolving world of genetics and genomics, can be taken free of charge for professional or personal development. Each module stands alone. Educators can work through the modules in sequence or move freely among them.

Center for Educational Outreach and Center for Collaborative and Interactive Technologies * (Baylor College of Medicine;)

2010-05-27

176

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures  

NASA Technical Reports Server (NTRS)

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

1984-01-01

177

Characterization of self-healing composite materials  

NASA Astrophysics Data System (ADS)

Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Researchers at the University of Illinois Urbana Champaign have recently developed a method to reverse the effects of, or heal, damage in the epoxy matrix. Their in-situ self-healing system uses embedded microcapsules and a catalyst that trigger a romp reaction in an effort to rebond the microcracks. Several models have been developed in an effort to predict how a composite laminate damages. One model in particular, the Continuous Damage Mechanics model, CDM that has been developed at West Virginia University uses material properties that are easily obtained from standard ASTM and ISO testing methods. The CDM model has been extended at West Virginia University to incorporate the effects of a self-healing system to develop a Continuous Damage and Healing Mechanics model, CDHM. In this work, a testing procedure to characterize the autonomic healing of polymer matrix composites is outlined, as well as the regenerative effects of the self-healing system. The capability of the CDHM model to predict the material properties of the self-healing system is also addressed. The CDHM model is validated with experimental results for various laminates fabricated out of E-glass/epoxy.

Ford, Kevin John

178

Natural porous agar materials from macroalgae.  

PubMed

Porous agar materials have been prepared from marine macroalgae species using a simple microwave-assisted extraction/drying methodology, providing a new family of polysaccharide derived porous solids. The microwave-assisted extraction allows a more efficient and less time-consuming extraction of the polysaccharide compared to conventional extraction protocols based on conventional heating. DRIFT and (13)C NMR results indicated that the internal agar structure (based on d-galactose and 3,6-anhydro-l-galactose linked units) was preserved after the extraction methodology, which opens a wide range of future possibilities and applications for this new family of porous polysaccharides. The extracted agar materials, which have already applications per se due to their high purities, could be subsequently transformed into a novel family of attractive mesoporous agar materials that could be used as natural templates for the production of nanocrystals of metal oxides. PMID:23399188

Francavilla, Matteo; Pineda, Antonio; Lin, Carol S K; Franchi, Massimo; Trotta, Pasquale; Romero, Antonio A; Luque, Rafael

2013-02-15

179

Natural Radioactivity of Quarry raw Material in Israel  

Microsoft Academic Search

During the past decade Natural Occurring Radioactive Material (NORM) has been receiving growing attention by radiation protection agencies, including chronic exposure to radon and radiation from building materials. A new Israeli standard (5098) which limit the radionuclide concentration in building material entered into force in 2003. Building materials are often made of natural raw materials which contain natural radionuclides from

G. Haquin; N. Gazit-Yaari; Z. Yungreis; M. Braun; M. Margaliot

2004-01-01

180

Viscoelastic models for polymeric composite materials  

NASA Astrophysics Data System (ADS)

An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the macroscopic behavior of the composite (explosive). Of interest here is the determination of an appropriate constitutive law for a polyurethane binder material. A Taylor Cylinder impact test, and uniaxial stress tension and compression tests at various strain rates, have been performed on the polyurethane. Evident from time resolved Taylor Cylinder profiles, the material undergoes very large strains (>100%) and yet recovers its initial configuration. A viscoelastic constitutive law is proposed for the polyurethane and was implemented in the finite element, explicit, continuum mechanics code EPIC. The Taylor Cylinder impact experiment was simulated and the results compared with experiment. Modeling improvements are discussed.

Bardenhagen, S. G.; Harstad, E. N.; Foster, J. C.; Maudlin, P. J.

1996-05-01

181

Industry to Education Technical Transfer Program & Composite Materials. Composite Materials Course. Fabrication I Course. Fabrication II Course. Composite Materials Testing Course. Final Report.  

ERIC Educational Resources Information Center

These four reports provide details of projects to design and implement courses to be offered as requirements for the associate degree program in composites and reinforced plastics technology. The reports describe project activities that led to development of curricula for four courses: composite materials, composite materials fabrication I,

Massuda, Rachel

182

The spectroscopic study of building composites containing natural sorbents  

NASA Astrophysics Data System (ADS)

This work presents the results of FT-IR spectroscopic studies of heavy metal cations (Ag +, Pb 2+, Zn 2+, Cd 2+ and Cr 3+) immobilization from aqueous solutions on natural sorbents. The sorption has been conducted on sodium forms of zeolite (clinoptilolite) and clay minerals (mixtures containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. In the next part of the work both sorbents were used to obtain new building composites. It was proven those heavy metal cations' sorption causes changes in IR spectra of the zeolite and clay minerals. These alterations are dependent on the way the cations were sorbed. In the case of zeolite, variations of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular complexes 4-4-1 (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations (650-700 cm -1). In the instance of clay minerals, changes in the spectra occur at two ranges: 1200-800 cm -1 - the range of the bands assigned to asymmetric Si-O(Si,Al) and bending Al-OH vibrations and 3800-3000 cm -1 - the range of the bands originating from OH - groups stretching vibrations. Next results indicate possibilities of applying the used natural sorbents for the obtainment of new building materials having favourable composition and valuable properties. The zeolite was used for obtaining autoclaved materials with an addition of CaO, and the clay minerals for ceramic sintered materials with an addition of quartz and clinoptilolite were produced. FT-IR studies were also conducted on the obtained materials.

Krl, M.; Mozgawa, W.

2011-08-01

183

Combustion synthesis of advanced composite materials  

NASA Technical Reports Server (NTRS)

Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product morphology and properties. The use of an in situ liquid infiltration technique and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e., solids, liquids and gases, with varying physical properties e.g., volatility and thermal conductivity, on the microstructure and morphology of synthesized composite materials is discussed. Conducting the combustion synthesis reaction in a reactive gas environment to take advantage of the synergistic effects of combustion synthesis and vapor phase transport is also examined.

Moore, John J.

1993-01-01

184

Calcium phosphate-based composites as injectable bone substitute materials.  

PubMed

A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature. PMID:20336722

Low, Kah Ling; Tan, Soon Huat; Zein, Sharif Hussein Sharif; Roether, Judith A; Mourio, Viviana; Boccaccini, Aldo R

2010-07-01

185

Collected Extraterrestrial Materials: Constraints on Meteor and Fireball Compositions  

NASA Astrophysics Data System (ADS)

The bulk density and bulk porosity of IDPs and various meteorite classes show that protoplanet accretion and evolution were arrested at different stages as a function of parent body modification. The collected IDPs, micrometeorites and meteorites are aggregates of different structural entities that were inherited from the earliest times of solar system evolution. These structural entities and the extent of parent body lithification will determine the material strength of the meteoroids entering the Earth's atmosphere. There is a need for measurements of the material strength of collected extraterrestrial materials because they will in part determine the nature of the chemical interactions of descending meteors and fireballs in the atmosphere. High-precision determinations of meteor and fireball compositions are required to search for anhydrous, carbon-rich proto-CI material that has survived in the boulders of comet nuclei.

Rietmeijer, Frans J. M.; Nuth, Joseph A., III

186

A Reliability Analysis Approach to Fatigue Life Dispersion of Laminated Glass Fiber Composite Materials.  

National Technical Information Service (NTIS)

The statistical nature of the fatigue life of laminated glass fiber composite materials (FRP) is studied. Four different FRP laminates (satin woven FRP, plain woven FRP, roving woven FRP, and SMC laminated FRP) were used in the experiments. Unidirectional...

T. Tanimoto S. Amijima H. Ishikawa K. J. Miller R. F. Smith

1979-01-01

187

Notebook on Electromagnetic Properties of Composite Materials Below 1 GHz.  

National Technical Information Service (NTIS)

This report is the seventh in a series of reports on the electromagnetic properties of composites materials. The report quantitatively delineates: the vast differences in electromagnetic behavior exhibited by the principle composite materials (Graphite/ep...

D. R. Pflug J. A. Birken R. A. Wallenberg D. T. Auckland

1981-01-01

188

Filament Composite Material Landing Gear Program, Volume I.  

National Technical Information Service (NTIS)

The objective of this program was to explore the utility of boron composite materials in aircraft landing gear construction. The contract work statement required the design, fabrication and test of a boron composite material landing gear assembly intercha...

1972-01-01

189

Prediction of Material Damping of Laminated Polymer Matrix Composites.  

National Technical Information Service (NTIS)

In this study the material damping of laminated composites is derived analytically. The derivation is based on the classical lamination theory in which there are eighteen material constants in the constitutive equations of laminated composites. Six of the...

C. T. Sun J. K. Wu R. F. Gibson

1987-01-01

190

Degradation study of date palm fibre\\/polypropylene composites in natural and artificial weathering: mechanical and thermal analysis  

Microsoft Academic Search

Date palm leaves were compounded with polypropylene (PP) and UV stabilizers to form composite materials. The stability of the composites in natural weathering conditions of Saudi Arabia and in accelerated weathering conditions was investigated. The composites were found to be much more stable than PP under the severe natural weathering conditions of Saudi Arabia and in accelerated weathering trials. Compatibilized

B. F Abu-Sharkh; H Hamid

2004-01-01

191

Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 19. Leaching Characteristics of Composited Materials from Mine Waste-Rock Piles and Naturally Altered Areas near Questa, New Mexico  

USGS Publications Warehouse

The goal of this study is to compare and contrast the leachability of metals and the acidity from individual mine waste-rock piles and natural erosional scars in the study area near Questa, New Mexico. Surficial multi-increment (composite) samples less than 2 millimeters in diameter from five waste-rock piles, nine erosional-scar areas, a less-altered site, and a tailings slurry-pipe sample were analyzed for bulk chemistry and mineralogy and subjected to two back-to-back leaching procedures. The first leaching procedure, the U.S. Geological Survey Field Leach Test (FLT), is a short-duration leach (5-minute shaking and 10-minute settling) and is intended to leach readily soluble materials. The FLT was immediately followed by an 18-hour, end-over-end rotation leaching procedure. Comparison of results from the back-to-back leaching procedures can provide information about reactions that may take place upon migration of leachates through changing geochemical conditions (for example, pH changes), both within the waste-rock and scar materials and away from the source materials. For the scar leachates, the concentrations of leachable metals varied substantially between the scar areas sampled. The scar leachates have low pH (pH 3.2-4.1). Under these low-pH conditions, cationic metals are solubilized and mobile, but anionic species, such as molybdenum, are less soluble and less mobile. Generally, metal concentrations in the waste-rock leachates did not exceed the upper range of those metal concentrations in the erosional-scar leachates. One exception is molybdenum, which is notably higher in the waste-rock leachates compared with the scar leachates. Most of the waste-rock leachates were at least mildly acidic (pH 3.0-6.2). The pH values in the waste-rock leachates span a large pH range that includes some pH-dependent solubility and metal-attenuation reactions. An increase in pH with leaching time and agitation indicates that there is pH-buffering capacity in some of the waste-rock piles. As pH increased in the waste-pile leachates, concentrations of several metals decreased with increasing time and agitation. Similar pH-dependent reactions may take place upon migration of the leachates in the waste-rock piles. Bulk chemistry, mineralogy, and leachate sulfur-isotope data indicate that the Capulin and Sugar Shack West waste-rock piles are compositionally different from the younger Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles. The Capulin and Sugar Shack West piles have the lowest-pH leachates (pH 3.0-4.1) of the waste-pile samples, and the source material for the Capulin and Sugar Shack West piles appears to be similar to the source material for the erosional-scar areas. Calcite dissolution, in addition to gypsum dissolution, appears to produce the calcium and sulfate concentrations in leachates from the Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles.

Smith, Kathleen S.; Hageman, Philip L.; Briggs, Paul H.; Sutley, Stephen J.; McCleskey, R. Blaine; Livo, K. Eric; Verplanck, Philip L.; Adams, Monique G.; Gemery-Hill, Pamela A.

2007-01-01

192

Dental composites/glass ionomers: the materials.  

PubMed

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1292462

Bowen, R L; Marjenhoff, W A

1992-09-01

193

Separating Mixtures: How We Concentrate Natural Materials  

NSDL National Science Digital Library

This activity involves separating mixtures of minerals on the basis of their physical properties. Students are shown a piece of granite and see that it is clearly a mixture. Students will try to devise ways of separating some simple mixtures and then see how some of the same methods are used to separate real minerals from mixtures. Students will discover that many useful materials are found as part of mixtures. For example, salt is found in underground deposits mixed with sand and clay. The mixture is called rock salt. Minerals are chemicals found naturally in the Earth and many of them are very useful. To get at the useful minerals, we usually have to separate them from less-useful material which are often called gangue (pronounced gang) by miners.

194

Ceramic Matrix Composite (CMC) Materials Development  

NASA Technical Reports Server (NTRS)

Under the former NASA EPM Program, much initial progress was made in identifying constituent materials and processes for SiC/SiC ceramic composite hot-section components. This presentation discusses the performance benefits of these approaches and elaborates on further constituent and property improvements made under NASA UEET. These include specific treatments at NASA that significantly improve the creep and environmental resistance of the Sylramic(TM) Sic fiber as well as the thermal conductivity and creep resistance of the CVI Sic matrix. Also discussed are recent findings concerning the beneficial effects of certain 2D-fabric architectures and carbon between the BN interphase coating and Sic matrix.

DiCarlo, James

2001-01-01

195

ALL NATURAL COMPOSITE SANDWICH BEAMS FOR STRUCTURAL APPLICATIONS. (R829576)  

EPA Science Inventory

As part of developing an all natural composite roof for housing application, structural panels and unit beams were manufactured out of soybean oil based resin and natural fibers (flax, cellulose, pulp, recycled paper, chicken feathers) using vacuum assisted resin tran...

196

Composite Materials Research and Technology at NASA/MSFC  

NASA Technical Reports Server (NTRS)

The utilization of composite materials in the Space Shuttle and Advanced Space Transportation Programs is reviewed. Topics include goals and challenges, descriptions of multi-generational launch vehicles, and an overview of composite materials research and technologies that support program objectives. A brief discussion of planned composite materials research and technology concludes the presentation.

Ledbetter, Frank E., III

1999-01-01

197

On the contribution of natural and restored wetlands to changes in the concentration and composition of dissolved organic material in the Sacramento-San Joaquin Delta and San Francisco Estuary.  

NASA Astrophysics Data System (ADS)

The amount and quality of wetland-derived dissolved organic material (DOM) entering delta and estuary environments remains poorly characterized even though DOM has two roles of societal significance: 1) it supports estuarine foodwebs, commonly habitat for endangered species, and 2) it presents problems when it occurs in drinking water supplies, forming carcinogenic byproducts on treatment. The Sacramento-San Joaquin Delta is a source of drinking water for over 20 million people and contributes 80% of the DOM entering the San Francisco Estuary, nearly doubling the concentration of DOM in the influent river water. The majority of the Delta is composed of below-sea level peat islands maintained in agricultural production by continuous pumping of DOM-rich drain water into Delta channels. Previous studies have shown that changes in the composition of the DOM in water that passes through the Delta are not consistent with addition of peat island drain water, and are more consistent with addition of wetland-derived material, suggesting that wetlands may contribute substantially to DOM export to the Estuary. Although wetlands currently contribute only 14% of the Delta, restoration is planned that would more than double this area, potentially altering DOM quality and content in the Delta and Estuary waters. Over the past several years we have examined the seasonal variation in the quality of DOM added by a variety of wetland types and island drains within the Delta and Estuary. In the current study, thirteen sites were each sampled five times. To date, we have analyzed the samples to determine the content of hydrophobic DOM, characterize the UV absorbance and fluorescence properties, and quantify the susceptibility to biodegradation both before and after photo-exposure. Samples were humic-rich, averaging over 75% hydrophobic content and varying from 74 to 86% with the variation in hydrophobic content between samples corresponding to changes in the optical properties. Samples typically were refractory with respect to biodegradation, with an average of 11% of the DOM susceptible to biodegradation prior to photoexposure, but the range was from 1% to 48%. Following photoexposure, samples were generally more refractory rather than more labile. Wetland DOM was found to react to form more drinking water disinfection byproducts than influent waters, but some wetland types appeared to contribute fewer precursors. Seasonal variation in biodegradation and chemical parameters was much greater than variation among wetland types, and the peak of biodegradeability was not related to the seasonal peak in DOM. This suggests addition of DOM through the Delta is controlled by changes in the nature of the source material rather than changes in efficiency or extent of remineralization.

Bergamaschi, B.; Stepanauskas, R.; Fram, M.; Hollibaugh, J.; Fujii, R.

2002-12-01

198

The Contribution of Natural and Restored Wetlands to Changes in the Concentration and Composition of Dissolved Organic Material in the Sacramento-San Joaquin Delta and San Francisco Estuary  

NASA Astrophysics Data System (ADS)

The quantity and quality of wetland-derived dissolved organic material (DOM) entering delta and estuary environments remains poorly characterized, even though DOM has two roles of societal significance: 1) it supports estuarine foodwebs, which commonly are a habitat for endangered species, and 2) it presents problems when it occurs in drinking water supplies, because it forms carcinogenic byproducts when treated. The Sacramento-San Joaquin Delta is a source of drinking water for more than 20 million people and contributes 80% of the DOM entering the San Francisco estuary, nearly doubling the concentration of DOM in the influent river water. The majority of the Delta is composed of below-sea-level peat islands that are maintained in agricultural production by continuous pumping of DOM-rich drain water into Delta channels. Previous studies indicate that changes in DOM composition in water passing through the Delta are not consistent with the addition of peat island drain water, and are more consistent with the addition of wetland-derived material. Therefore, wetlands may contribute substantially to DOM export to the estuary. Although wetlands currently constitute only 14% of the Delta, restoration is planned that would more than double this wetland area, potentially altering DOM quality and content in the Delta and estuary waters. During the past several years, the seasonal variation in the quality of DOM added by a variety of wetland types and island drains within the Delta and estuary has been examined. In this study, 13 sites were sampled 5 times. As of September 2002, the samples have been analyzed to determine the content of hydrophobic DOM, characterize the ultraviolet absorbance and fluorescence properties, and quantify the susceptibility to biodegradation before and after photoexposure. Samples were humic-rich, averaging more than 75% hydrophobic content and varying from 74 to 86%, with the variation in hydrophobic content between samples corresponding to changes in the optical properties. Samples typically were refractory with respect to biodegradation, having an average of 11% of the DOM being susceptible to biodegradation prior to photoexposure, but the range was from 1% to 48%. Following photoexposure, samples generally were more refractory rather than more labile. Wetland DOM reacted to form more drinking water disinfection byproducts than influent waters, but some wetland types seemed to contribute fewer precursors. Seasonal variation in biodegradation and chemical parameters was much greater than variation among wetland types, and the peak of biodegradability was not related to the seasonal peak in DOM. Therefore, the addition of DOM through the Delta is controlled by changes in the nature of the source material rather than changes in efficiency or extent of remineralization.

Bergamaschi, B. A.; Stepanauskas, R.; Fram, M.; Hollibaugh, J. T.; Fujii, R.

2002-12-01

199

Radiation Facilities for Composite Materials Formation  

NASA Astrophysics Data System (ADS)

The radiation facilities on the base of linac for polymer composite materials (PCM) formation was designed. The general technological scheme of PCM production consists in impregnations by synthetic monomers or oligomers of wares made of capillaryporous materials such as wood, qypsum, concrete, ceramic, paper, waste of papermaking, textile and woodworking production which are further treated by relativistic electron or breamsstruhglung beams. The facilities encorporates a linac with scanning electron beams, microwave chamber for drying of materials, a system for vacuum impregnating of materials with synthetic origomers, test bench for irradiations of samples, precise monitoring system for measuring of three-dimentional dose distribution in irradiated samples, and control processing system. The main beam parameters of linac are: electron energy 5--8 MeV; mean beam power up to 5 kW, pulse duration 1--4 mcs; scanning frequency of electromagnetic scanner 1--8 Hz; the irradiation is possible both with electron and with breamsstrahglung beams. The facilities were used for radiation processing investigation and production of new high-strength and corrosian-resistant PCM.

Popov, G. F.; Zalubovsky, I. I.; Avilov, A. M.; Rudychev, V. G.

1997-05-01

200

New topics on nanoindentation of polymers and composite materials  

NASA Astrophysics Data System (ADS)

In this study, nanoindentation was used to determine Young's modulus of homogeneous plastic materials as well as inhomogeneous epoxy woven fabric composites using various indenters. In the first part, homogeneous PMMA and polycarbonate were characterized using conical and spherical indenters. The conventional approach of the inverse analysis was modified in order to account for effects obtained during spherical nanoindentation. The experimental results were verified using FEA analysis in ABAQUS. It was found that viscous effects were present in conical nanoindentations which led to an overestimation of contact stiffness. The second part, the response of carbon and glass fiber woven fabric epoxy composites was investigated using Berkovich and spherical indenters. Localized nanoindentation was performed using the Berkovich probe in both materials which led to determination of glass fibers and matrix stiffnesses. The anisotropic nature of the response was treated modifying the classical approach to calculate transverse modulus of a unidirectional composite. Finally, fiber volume ratios were calculated according to type of composite and indenter used.

Martinez Hernandez, Ricardo

201

PROPERTIES OF RICE HUSK POWDER\\/NATURAL RUBBER COMPOSITE  

Microsoft Academic Search

The effects of epoxidized natural rubber (ENR) on cure characteristics, mechanical properties, and swelling behavior of rice husk powder (RHP) filled natural rubber (NR) composite were studied. Results indicated that the scorch time t2 and cure time t90 of the composite decrease with increasing filler loading and with presence of a ENR. Minimum torque also increases with increasing filler loading

Razif Nordin; H. Ismail

202

High velocity impact resistance of composite materials  

NASA Astrophysics Data System (ADS)

Composite materials are used in applications that require protection against high velocity impacts by fragment simulating projectiles. In this work, the ballistic performance of two commercially available materials against a fragments simulating projectile (FSP) is studied. The materials used were an aramid fiber with a phenolic matrix and a polyethylene fiber with a thermoplastic film. Impact tests have been carried out, with velocities ranging from 300 m/s to 1260m/s. The projectile used is a 1.1g NATO FSP. Impact velocity and exit velocity are measured, to determine the V{50} and the energy absorbed in cases where perforation occurs. Assessment of the impact damaged area is done using ultrasonic C-scan inspection. Types of damage and damage mechanisms have been identified. Several mechanical tests have been carried out to determine the mechanical properties, at different strain rates. Future work in numerical simulation of impact will be done using commercial code AutodyntinycircledR ftom Century Dynamics.

Justo, Jo; Marquer, A. T.

2003-09-01

203

Properties of natural fiber composites made by pultrusion process  

Microsoft Academic Search

Great efforts are being made at Brunel University, UK in attempt to develop natural fiber composites with desired structure and good overall properties for construction. This work focuses on the mechanical and morphological characterization of the pultruded composite rods made from hemp and wool fiber reinforcements. The results showed that the composite using polyurethane resin system has higher specific tensile

Xi Peng; Mizi Fan; John Hartley; Majeed Al-Zubaidy

2012-01-01

204

Nature of branching in disordered materials  

NASA Astrophysics Data System (ADS)

The phenomenon of structural branching is ubiquitous in a wide array of materials such as polymers, ceramic aggregates, networks and gels. These materials with structural branching are a unique class of disordered materials and often display complex architectures. Branching has a strong influence over the structure-property relationships of these materials. Despite the generic importance across a wide spectrum of materials, our physical understanding of the scientific nature of branching and the analytic description and quantification of branching is at an early stage, though many decades of effort have been made. For polymers, branching is conventionally characterized by hydrodynamic radius (size exclusion chromatography, SEC, rheology) or by counting branch sites (nuclear magnetic resonance spectroscopy, NMR). SEC and rheology are, at best, qualitative; and quantitative characterization techniques like NMR and transmission electron microscopy (TEM) (for ceramic nanoparticulate aggregates) have limitations in providing routine quantification. Effective structure characterization, though an important step in understanding these materials, remains elusive. For ceramic aggregates, theoretical work has dominated and only a few publications on analytic studies exist to support theory. A new generic scaling model is proposed in Chapter I, which encompasses the critical structural features associated with these complex architectures. The central theme of this work is the application of this model to describe a variety of disordered structures like aggregated nano-particulates, long chain branched polymers like polyethylene, hyperbranched polymers, multi-arm star polymers, and cyclic macromolecules. The application of the proposed model to these materials results in a number of fundamental structural parameters, like the mass-fractal dimension, df, the minimum path dimension, dmin, connectivity dimension, c, and the mole fraction branch content, ?br. These dimensions reflect different features of the global structure, and it is categorically shown that this dimensional analysis results in effective structure characterization of these materials. Small-angle scattering of x-rays and neutrons can be used to quantify branch content and characterize the structure, through application of concepts native to fractal geometry. The application of the scaling model to nano-particulate aggregates yields quantitative information regarding the structure of these materials. In-situ small and ultra small angle x-ray scattering data collected on fumed silica and soot particles is presented in Chapter II. These measurements were performed at Advanced Photon Source, Argonne National Laboratory, UNICAT beam-line and the European Synchrotron Radiation Facility, Grenoble, France, ID2 beam-line. The dimensional analysis is successful in not only giving an average snap-shot of the nano-particulate aggregates, but also yields information regarding the growth processes involved in the complex pyrolysis technique of synthesizing these materials. In case of macromolecular systems, the minimum path dimension, dmin, is shown to reflect the thermodynamics of the system. This is categorically established in Chapter III on hyperbranched polymers, where the scaling model accurately predicts the good-solvent to theta-condition transition in these highly branched polymers with increasing molar mass. The scaling model is applied to the long standing problem of quantifying long chain branching in polyethylene in Chapter IV. Small angle neutron scattering data on dilute solutions of polyethylene were obtained at the Intense Pulsed Neutron Source (SAND beam-line); NIST center for Neutron Scattering (NG3 beam-line); and Los Alamos Neutron Scattering Center (LQD beam-line). This work, for the first time in literature, reports the length of a long chain branch in polyethylene in terms of the average molar mass of the branches, and the average number of carbon atoms in the long chain branch. Cyclic polymers are examined in the Chapter V. The scaling model presents a new

Kulkarni, Amit S.

205

Fiber optics in composite materials: materials with nerves of glass  

NASA Astrophysics Data System (ADS)

A Fiber Optic BasedSmart Structure wiipossess a structurally integrated optical microsensor system for determining its state. This built-in sensor system should, in real-time, be able to: evaluate the strain or deformation of a structure, monitor if its vibrating or subject to excessive loads, check its temperature and warn of the appearance of any hot spots. In addition a Smart Structure should maintain a vigilant survelliance over its structural integrity. The successful development of Smart StructureTechnolgy could lead to: aircraft that are safer, lighter, more efficient, easier to maintain and to service; pipelines, pressure vessels and storage tanks that constantly monitor their structuralintegrity and immediately issue an alert ifany problem is detected; space platforms that check forpressure leaks, unwanted vibration, excess thermal buildup, and deviation from some preassigned shape.This technology is particularly appropriate for composite materials where internal damage generated by: impacts, manufacturing flaws, excessive loading or fatigue could be detected and assessed. In service monitoring of structural loads, especially in regions like wing roots of aircraft, could be ofconsiderable benefit in helping to avoid structural overdesign and reduce weight. Structurally imbedded optical fibers sensors might also serve to monitor the cure state of composite thermosets during their fabrication and thereby contribute to improved quality control of these products.

Measures, Raymond M.

1990-08-01

206

Thermophysical Analysis of High Modulus Composite Materials for Space Vehicles  

NASA Astrophysics Data System (ADS)

High modulus composite materials are used extensively in aerospace vehicles mainly for the purpose of increasing strength and reducing weight. However, thermal properties have become essential design information with the use of composite materials in the thermal design of spacecraft and spacecraft electronics packages. This is because the localized heat from closely packed devices can lead to functional failure of the aerospace system unless the heat is dissipated. In this study, thermal responses of high modulus advanced materials are considered for aerospace thermal design. The advanced composite material is composed of a continuous high modulus pitch based fiber and epoxy resin. In order to compare this advanced composite material with conventional aerospace composite materials, the thermophysical analysis of both materials was performed. The results include thermal conductivity measurements of composite materials and various thermal analytical techniques with DSC, TGA, TMA and DMA.

Lee, Ho-Sung

2009-01-01

207

Electromagnetic Shielding Efficiency Measurement of Composite Materials  

NASA Astrophysics Data System (ADS)

This paper deals with the theoretical and practical aspects of the shielding efficiency measurements of construction composite materials. This contribution describes an alternative test method of these measurements by using the measurement circular flange. The measured results and parameters of coaxial test flange are also discussed. The measurement circular flange is described by measured scattering parameters in the frequency range from 9 kHz up to 1 GHz. The accuracy of the used shielding efficiency measurement method was checked by brass calibration ring. The suitability of the coaxial test setup was also checked by measurements on the EMC test chamber. This data was compared with the measured data on the real EMC chamber. The whole measurement of shielding efficiency was controlled by the program which runs on a personal computer. This program was created in the VEE Pro environment produced by Agilent Technology.

D?novsk, J.; Kejk, Z.

2009-01-01

208

Method of preparing corrosion resistant composite materials  

DOEpatents

Method of manufacture of ceramic materials which require stability in severely-corrosive environment having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These surfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

Kaun, Thomas D. (320 Willow St., New Lenox, IL 60451)

1993-01-01

209

Effective thermal conduction in composite materials  

NASA Astrophysics Data System (ADS)

The problem of determining the bounds and/or estimating the effective thermal conductivity ( ? eff) of a composite (multiphase) system given the volume fractions and the conductivities of the components has been investigated. A comparison between the measured data and the results predicted by theoretical models has been made for seven heterogeneous samples. The tested models include those of the effective medium theory (EMT), Hashin and Shtrikman (HS) bounds, and Wiener bounds. These models can be used to characterize macroscopic homogeneous and isotropic multiphase composite materials either by determining the bounds for the effective thermal conductivity and/or by estimating the overall conductivity of the random mixture. It turns out that the most suitable one of these models to estimate ? eff is the EMT model. This model is a mathematical model based on the homogeneity condition which satisfies the existence of a statistically homogeneous medium that encloses inclusions of different phases. Numerical values of thermal conductivity for the samples that satisfy the homogeneity condition imposed by the effective medium theory are in best agreement with the experimentally measured ones.

Suleiman, Bashir M.

2010-04-01

210

Identification of failure modes in composite materials  

NASA Astrophysics Data System (ADS)

Recently a new structural health monitoring system that employs a "continuous acoustic emission sensor" and an embeddable local processor has been proposed. The development of a processor that integrates the functions of signal conditioning, feature extraction, data storage, and digital communication is currently in progress. A prototype of this local processor chip has been developed. The integration of a continuous sensor with an embeddable local processor can potentially enable an inexpensive method of monitoring large and complex structures using acoustic emission signals. Such a system can reduce the cost, complexity, and weight of the required instrumentation. It is potentially scalable to large and complex structures and could be integrated into the structural material. The success of the acoustic emission based structural health monitoring technique depends on its ability to discriminate between valid acoustic emission signals and ambient noise. In addition, the technique should be able to identify the damage mode from the acoustic emission waveforms. This paper focuses on the use of acoustic emission technique for the identification of failure modes in composite materials. Three types of failure modes in glass fabric epoxy composite laminates are considered. These are two types of delamination growth and transverse crack growth. Wavelet analysis is used to extract time frequency information from the acoustic emission signals. Different features of the waveform including the frequency components, Symmetric and Antisymmetric components, and amplitudes are used to classify the signals and identify the failure modes. The laboratory tests indicate that it is possible to distinguish the individual failure modes under consideration. It was also possible to filter out spurious AE signals that originate from extraneous sources using an appropriate choice of sensors and frequency components. An attempt is made to relate the rate of damage growth with the detected acoustic emission signal parameters.

Nkrumah, F.; Grandhi, G.; Sundaresan, M. J.; Derriso, M.

2005-05-01

211

New High Performance Natural Fiber Composites  

Microsoft Academic Search

Cellulose fiber composites have been used ex- tensively for the construction industries in North Ameri- ca and they began to receive very much attraction in Eu- rope, South America and Asia. In order to increase the competitiveness, it is important for the composites indus- try to reduce the consumption of energy and cost as well as to improve output and

J. Denault; F. Perrin; W. Hu

212

Maleated natural rubber as a coupling agent for paper sludge filled natural rubber composites  

Microsoft Academic Search

Paper sludge filled natural rubber composites were prepared by incorporation of different loadings (1040phr) of paper sludge fillers. Two series of composites were studied, i.e. composites with and without maleic anhydride grafted natural rubber (MANR). Grafting of maleic anhydride onto the natural rubber was done prior to compounding using an internal mixer. The curing characteristics, dynamic properties and tensile properties

H. Ismail; A. Rusli; A. A. Rashid

2005-01-01

213

Composite materials testing for remotely piloted vehicles. Memorandum report  

SciTech Connect

The purpose of this report is to test and evaluate the material properties of composites, built by Code 5712 of the Naval Research Laboratory, for use on Remotely Piloted Vehicles (RPV's). These composite materials are generally combinations of Balsa wood and Kevlar or Fiberglas, using Epoxy as a binder. The specific requirement of these composites necessitate that the weight of the material be kept at a minimum. In accordance with this requirement, a fabrication procedures was adopted that deviates from that traditionally established in the composites field. The main difference is that, in the construction of these composites no dam is used to surround the material while the epoxy cures. Conventional composite fabrication procedures use a dam to prevent epoxy (resin) from migrating away from the material. This fabrication process was examined in relation to it's effects on the material properties of these composites.

Quraishi, N.

1989-01-25

214

Metal inserts in structural composite materials manufactured by RTM  

Microsoft Academic Search

Load transfer on a structural composite part can be carried out by means of metal inserts. Apart from their detachable features, their introduction in a composite material is not without consequence. This paper examines the impact of the inserts in a structural composite material obtained by the Resin Transfer Moulding process. Numerical flow simulations, using RTMFLOT software developed by the

B. Ferret; M. Anduze; C. Nardari

1998-01-01

215

Composite materials: Tomorrow for the day after tomorrow  

NASA Technical Reports Server (NTRS)

A description is given of the history of the use of composite materials in the aerospace industry. Research programs underway to obtain exact data on the behavior of composite materials over time are discussed. It is concluded that metal composites have not yet replaced metals, but that that this may be a future possibility.

Condom, P.

1982-01-01

216

Composite Materials: Tomorrow for the Day after Tomorrow.  

National Technical Information Service (NTIS)

A description is given of the history of the use of composite materials in the aerospace industry. Research programs underway to obtain exact data on the behavior of composite materials over time are discussed. It is concluded that metal composites have n...

P. Condom

1982-01-01

217

Millimeter-wave imaging of composite materials  

SciTech Connect

This work addresses the application and evaluates the potential of mm-wave imaging in the W-band (75-110 GHz) using samples of low-loss dielectric and composite materials with artificial defects. The initial focus is on the measurement of amplitude changes in the back scattered and forward-scattered fields. The c-scan system employs a focused beam antenna to provide spatial resolution of about one wavelength. A plane-wave model is used to calculate the effective reflection (or transmission) coefficient of multilayer test sample geometry. Theoretical analysis is used to optimize the measurement frequency for higher image contrast and to interpret the experimental results. Both reflection and transmission images, based on back scattered and forward-scattered powers, were made with Plexiglas and Kevlar/epoxy samples containing artificially introduced defects such as subsurface voids and disbonds. The results clearly indicate that mm-wave imaging has high potential for non-contact interrogation of low-loss materials.

Gopalsami, N.; Bakhtiari, S.; Dieckman, S.L.; Raptis, A.C.; Lepper, M.J.

1993-09-01

218

Processing and characterization of natural cellulose fibers/thermoset polymer composites.  

PubMed

Recently natural cellulose fibers from different biorenewable resources have attracted the considerable attraction of research community all around the globe owing to their unique intrinsic properties such as biodegradability, easy availability, environmental friendliness, flexibility, easy processing and impressive physico-mechanical properties. Natural cellulose fibers based materials are finding their applications in a number of fields ranging from automotive to biomedical. Natural cellulose fibers have been frequently used as the reinforcement component in polymers to add the specific properties in the final product. A variety of cellulose fibers based polymer composite materials have been developed using various synthetic strategies. Seeing the immense advantages of cellulose fibers, in this article we discuss the processing of biorenewable natural cellulose fibers; chemical functionalization of cellulose fibers; synthesis of polymer resins; different strategies to prepare cellulose based green polymer composites, and diverse applications of natural cellulose fibers/polymer composite materials. The article provides an in depth analysis and comprehensive knowledge to the beginners in the field of natural cellulose fibers/polymer composites. The prime aim of this review article is to demonstrate the recent development and emerging applications of natural cellulose fibers and their polymer materials. PMID:24815407

Thakur, Vijay Kumar; Thakur, Manju Kumari

2014-08-30

219

Highly birefringent polymer microstructured optical fibers embedded in composite materials  

NASA Astrophysics Data System (ADS)

Composite structures are made from two or more constituent materials with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing highly birefringent polymer microstructured optical fibers into the composite material. These new fibers can consist of only two polymer materials (PMMA and PC) with similar value of the Young modulus as the composite material so any stresses induced in the composite material can be easily measured by the proposed embedded fiber optic sensors.

Lesiak, P.; Szel g, M.; Kuczkowski, M.; Doma?ski, A. W.; Woli?ski, T. R.

2013-05-01

220

A Review on the Natural Fiber-Reinforced Polymer Composites for the Development of Roselle Fiber-Reinforced Polyester Composite  

Microsoft Academic Search

In recent years, the interest of scientists and engineers has turned over on utilizing all plant fibers as effectively and economically as possible to produce good quality fiber-reinforced polymer composites for structural, building, and other needs. It is because of the high availability of the natural resources in this green world. This has led to the development of alternative materials

M. Thiruchitrambalam; A. Athijayamani; S. Sathiyamurthy; A. Syed Abu Thaheer

2010-01-01

221

Discrimination of naturally occurring radioactive material in plastic scintillator material  

Microsoft Academic Search

Plastic scintillator material is used in many applications for the detection of gamma rays from radioactive material, primarily due to the sensitivity per unit cost compared to other detection materials. However, the resolution and lack of full-energy peaks in the plastic scintillator material prohibits detailed spectroscopy. Therefore, other materials such as doped sodium iodide are used for spectroscopic applications. The

J. H. Ely; R. T. Kouzes; B. D. Geelhood; J. E. Schweppe; R. A. Warner

2004-01-01

222

Power Composites: Structural Materials that Generate and Store Electrical Energy.  

National Technical Information Service (NTIS)

We describe progress in the development of a synthetic multifunctional material: namely a fiber composite with both power and structural function. The structural composite contains batteries encased in piezoelectric tubes. When the structure vibrates the ...

D. A. Shockey S. C. Ventura S. C. Narang J. W. Simons B. C. Bourne

2005-01-01

223

Soviet Developments in Composite Materials, January - June 1975.  

National Technical Information Service (NTIS)

Selected Soviet publications on composite materials over a period of 6 months (January to June 1975) are abstracted in this report. The publications cover both experimental and theoretical research on carbon fiber-reinforced plastic composites and carbon ...

J. Kourilo

1976-01-01

224

Composite materials with metallic matrix and ceramic porous filler  

Microsoft Academic Search

Composite materials with a reduced density reinforced with hollow corundum particles can be of interest as damping and abrasive materials for decreasing the mass of a structure. Methods for mixing powders and their hot pressing are suggested in order to produce such composite materials without fracture of the brittle hollow particles of the filler.

V. I. Bakarinova; V. K. Portnoi

1995-01-01

225

Compendium of Material Composition Data for Radiation Transport Modeling  

Microsoft Academic Search

Introduction Meaningful simulations of radiation transport applications require realistic definitions of material composition and densities. When seeking that information for applications in fields such as homeland security, radiation shielding and protection, and criticality safety, researchers usually encounter a variety of materials for which elemental compositions are not readily available or densities are not defined. Publication of the Compendium of Material

Ronald J. McConn; Christopher J. Gesh; Richard T. Pagh; Robert A. Rucker; Robert Williams

2011-01-01

226

The simulation of composite material response under dynamic compressive loading  

Microsoft Academic Search

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behaviour under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the

S. A. Silling; P. A. Taylor

1994-01-01

227

Simulation of composite material response under dynamic compressive loading  

Microsoft Academic Search

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the

S. A. Silling; P. A. Taylor

1993-01-01

228

A multi-continuum theory for composite elastic materials  

Microsoft Academic Search

Summary A continuum theory for composite materials is presented in which the composite constituents are modeled by superimposed continua which undergo thermal and mechanical interactions. Kinematical notions, field equations and a constitutive theory are developed, including consequences of material frame indifference and material symmetry which restrict the form of the response functions. The final result is a set of linearized

A. Bedford; M. Stern

1972-01-01

229

The failure mode of natural silk epoxy triggered composite tubes  

NASA Astrophysics Data System (ADS)

In this study the quasi static compression test over natural silk epoxy triggered composite tubes has been carried out, the natural silk epoxy composite tubes consist of 24 layer of woven natural silk as reinforcement and thermoset epoxy resin as matrix which both of them i e natural silk and epoxy have excellent mechanical properties More over the natural silk have better moisture resistance in comparison with other natural reinforcements, the length of tubes are 50, 80 and 120 mm The natural silk epoxy composite tubes are associated with an external trigger which includes 4 steel pieces welded on downside flat plate fixture The hand lay up fabrication method has been used to make the natural silk epoxy composite tubes Instron universal testing machine with 250 KN load capacity has been employed to accomplish this investigation The failure modes of natural silk epoxy triggered composite tubes has been investigated by representative photographs which has been taken by a high resolution camera(12 2 Mp) during the quasi static compression test, from the photographs is observed the failure modes is progressive local buckling

Eshkour, R. A.; Ariffin, A. K.; Zulkifli, R.; Sulong, A. B.; Azhari, C. H.

2012-09-01

230

Thermoelectric study of INSB secondary phase based nano composite materials  

NASA Astrophysics Data System (ADS)

In the past several decades there has been an intensive study in the field of thermoelectric study that is basically materials driven. As the simplest technology applicable in direct heat-electricity energy conversion, thermoelectricity utilizes the Seebeck effect to generate electricity from heat or conversely achieve the solid-state cooling via the Peltier effect. With many technical merits, thermoelectric devices can be used as spot-size generators or distributed refrigerators, however, their applications are restricted by the energy conversion efficiency, which is mainly determined by the figure of merit ZT of the thermoelectric materials that these devices are made of. A higher ZT (ZT=alpha2*sigma/kappa) entails a larger Seebeck coefficient (alpha), a higher electrical conductivity (sigma) and a lower thermal conductivity (kappa). However, it is challenging to simultaneously optimize these three material parameters because they are adversely correlated. To this end, a promising approach to answer this challenge is nano-compositing or microstructuring at multiple length scales. The numerous grain boundaries in nano-composite allow for significant reduction of lattice thermal conductivity via strong phonon scattering and as well an enhanced Seebeck coefficient via, carrier energy filtering effect. As the same grain boundaries also scatter carriers, a coherent interface between grains is needed to minimize the degradation of carrier mobilities. To this end,in-situ, instead of ex-situ, formation of nano-composite is preferred. It is noteworthy that electrical conductivity can be further enhanced by the injection of high-mobility carriers introduced by the secondary nano-phase. In view of the prevalent use of Antimony (Sb) in thermoelectric materials, Indium Antimonide (InSb) naturally becomes one of the most promising nano-inclusions since it possesses one of the largest carrier mobilities (7.8 m 2/V-s) in any semiconductors, while at the same time possesses a reasonably narrow band gap (0.17 eV at 300 K). In this dissertation, I experimentally investigate whether InSb could be a "good" nano-secondary phase in two thermoelectric bulk matrix materials, FeSb2 and half-Heusler compounds. In these in situ formed nano-composites, three mechanisms are utilized to decouple the otherwise adversely correlated Seebeck coefficient (alpha), electrical conductivity (sigma), and thermal conductivity (kappa). First, low energy carriers will be filtered out via the carrier energy filtering effect, enhancing the Seebeck coefficient without degrading the power factor (PF= alpha 2sigma). Second, high mobility carriers from the InSb nano-inclusions will be injected to the system to increase the electrical conductivity. Last, the numerous grain boundaries present in nano-composites allow for strong phonon scattering so as to reduce the thermal conductivity. After the initial in situ synthesis of nano-composites with the optimized composition, further nano-structuring processes are applied in the samples of FeSb2 with 0.5% atomic ratio of InSb. The results indicate that not all nano-structures are thermoelectrically favorable, multi-scale microstructures with the length scale comparable with the phonon mean free path are needed to effectively scatter phonons over a wide range of wavelength. In summary, the successful combination of the carrier energy filtering effect, high mobility carrier injection effect, and strong phonon scattering effect in the in situ synthesized FeSb2-InSb and half-Heusler-InSb nano-composites leads to a significantly enhanced ZT. This approach of in situ formation of nano-composites based on InSb secondary nano-phase may also be applied to other thermoelectric materials.

Zhu, Song

231

Flame Resistant Insulation Materials, Composition and Method.  

National Technical Information Service (NTIS)

This patent application concerns flame retardancy of loosefill insulation materials, especially cellulosic insulation materials. More particularly, the invention relates to flame resistant insulation materials, methods of treating insulation materials to ...

R. J. McCarter

1980-01-01

232

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.  

PubMed

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

233

Preparation and performances of a novel intelligent humidity control composite material  

Microsoft Academic Search

A novel intelligent humidity control composite material with excellent humidity control performances has been prepared, comprising a natural polymer derivative (carboxymethyl cellulose (CMC)), a porous natural mineral (sepiolite), and an acrylic acid (AA)\\/acrylamide (AM) copolymer. It features high moisture adsorption capacity, fast response to humidity changes, small equilibrium humidity control range and good acid gas absorbability. It is suitable for

Hailiang Yang; Zhiqin Peng; Yang Zhou; Feng Zhao; Jing Zhang; Xiaoye Cao; Zhiwen Hu

2011-01-01

234

An Evaluation of the Oxygen Compatibility of Composite Materials  

NASA Technical Reports Server (NTRS)

Three tests are described which evaluate the oxygen compatibility characteristics of multiple composite materials: 1) Mechanical Impact Bruceton 'Up and Down' Method; 2) Promoted Combustion; 3) Electrostatic Discharge.

Richardson, Erin H.; Hall, Joylene

2003-01-01

235

CCMR: Green Composites: An alternative to petroleum-based materials  

NSDL National Science Digital Library

Composites made from natural fibers and resins offer a potential alternative to the petroleum-based materials that are currently used in in many applications such as packaging. These composites have the advantage of being biodegradable, renewable and environmentally friendly. In this work, different additives, including glycerol and polycarboxylic acid (PCA), are introduced to these composites in an attempt to increase properties such as strength and flexibility.

Cooley, Ladean M.

2007-08-29

236

Hysteresis heating based induction bonding of composite materials  

NASA Astrophysics Data System (ADS)

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni/PSU). An excellent heating rate can be attained in the frequency range of 1 to 10 MHz for particle volume fraction below percolation of 0.26. The diameter of nickel particle should be kept between 65 nm to 10 mum to ensure multi-domain heating, Curie temperature control, negligible shielding effect, minimum eddy current, and slight particle oxidation. The hysteresis heating behavior of the Ni/PSU films is found to be volumetric in nature and proportional to the cube of applied magnetic field. On the other hand, heat generation is inversely proportional to the size of the multi-domain particles. The frequency effect; however, provide maximum heat generation at the domain wall resonance frequency. Curie temperature control is observed when sufficiently high magnetic fields (138 Oe) are applied. The master curves of AC heat generation in Ni/PSU films are established and show a strong particle size effect. Hysteresis fusion bonding of glass/polyphenylene sulfide thermoplastic composites using a magnetic film as the thermoplastic adhesive shows that the bond strength of hysteresis-welded materials is comparable to that of autoclave-welded materials while offering an order of magnitude reduction in cycle time. The relative contribution of the intimate contact and healing mechanisms to the fusion bonding process indicates that hysteresis bonding is controlled by intimate contact. The macroscopic failure modes vary from mostly adhesive composite/film (low bond strength) to a combination of adhesive composite/film, cohesive film, cohesive composite and mostly cohesive composite (high bond strength). Inspection of the microscopic failure at the nickel particle/polymer interface in the film indicates quasi-brittle failure mode. The amount of adhesive failure increases with decreasing particle size and increasing particle volume fraction. The XPS peaks confirm nickel oxide in the form of NiO on the failure surface of particle/polymer debonding of hysteresis susceptor film.

Suwanwatana, Witchuda

237

ROLE OF FIBER MODIFICATION IN NATURAL FIBER COMPOSITE PROCESSING  

Microsoft Academic Search

The prediction and characterization of the adhesion between fiber, surface treatment, and polymer is critical to the success of large-scale natural fiber based polymer composites in automotive semi-structural application. The two primary factors limiting the use of natural fiber in polymer composites are fiber moisture uptake and fiber degradation during high-temperature processing. In this study, we have developed several fiber

Leonard S. Fifield; Kayte M. Denslow; Anna Gutowska; Kevin L. Simmons; Jim Holbery

2005-01-01

238

Material composition optimization for heat-resisting FGMs by artificial neural network  

Microsoft Academic Search

Unless the material composition field in functionally graded materials (FGM) is assumed a priori, an explicit relation between the objective function and the design variables is almost hard to derive. This implicitness naturally leads to the use of finite difference scheme for the sensitivity analysis in the numerical optimization, but which requires the remarkably long CPU time when the objective

J. R. Cho; S. W. Shin

2004-01-01

239

Surface composites: A new class of engineered materials  

SciTech Connect

To integrate irreconcilable material properties into a single component, a new class of engineered materials termed {open_quotes}surface composites{close_quotes} has been developed. In this engineered material, the second phase is spatially distributed in the near surface regions, such that the phase composition is linearly graded as a function of distance from the surface. Surface composites are different from existing engineered materials such as {open_quotes}bulk composites{close_quotes} and {open_quotes}functionally graded materials{close_quotes} (FGM). Unlike bulk composites, the surface phase in surface composites is present only at the near surface regions. In contrast to FGM, the graded properties of surface composites are achieved by unique morphological surface modification of the bulk phase. To fabricate surface composites, the initial surface of the bulk material is transformed using a novel multiple pulse irradiation technique into truncated cone-like structures. The laser induced micro-rough structures (LIMS) possess surface areas which are up to an order of magnitude higher than the original surface. The second phase is deposited on the surface using thin or thick film deposition methods. A key characteristic of surface composites is the formation of a three dimensional, compositionally and thermally graded interface, which gives rise to improved adhesion of the surface phase. Examples of various types of surface composites such as W/Mo, silica/SiC and diamond/steel, etc. are presented in this paper. The unique properties of surface composites make them ideal engineered materials for applications involving adherent thick film coatings of thermally mismatched materials, compositional surface modification for controlled catalytic activity, and creating adherent metal-ceramic and ceramic-polymeric joints. {copyright} {ital 1997 Materials Research Society.}

Singh, R.; Fitz-Gerald, J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

1997-03-01

240

Nanostructured Composite Materials for High Temperature Thermoelectric Energy Conversion.  

National Technical Information Service (NTIS)

The goals of this project were to synthesize, characterize and model bulk nanostructured composite materials for thermoelectric energy conversion applications. The objective was to produce materials which demonstrate an increase in intrinsic thermoelectri...

C. J. O'Connor

2012-01-01

241

Effect of Sericin on Mechanical Behavior of Composite Material Reinforced by Silk Woven Fabric  

NASA Astrophysics Data System (ADS)

Recent, attention has been given to shift from glass fibers and carbon fibers to natural fibers for FRP composites for the goal of protecting the environment. This paper concerned with the application of silk fabric for composite materials. Polypropylene (PP) was used for the matrix material and the silk fabric composites were molded using a compression molding method. Especially, the effect of sericin on mechanical behaviors of composite materials was discussed. Good adhesion between silk and PP was obtained by removing the sericin existing around the fibroin. The tensile modulus of composite decreased with decreasing the sericin because of the flexibility of silk fibers without sericin. In particular, the higher Izod impact value was obtained for the composites containing the silk fibers without sericin.

Kimura, Teruo; Ino, Haruhiro; Hanada, Koji; Katori, Sigetaka

242

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Dai, Heming

243

Double Cantilever Beam Fracture Toughness Testing of Several Composite Materials  

NASA Technical Reports Server (NTRS)

Double-cantilever beam fracture toughness tests were performed by the Composite Materials Research Group on several different unidirectional composite materials provided by NASA Langley Research Center. The composite materials consisted of Hercules IM-7 carbon fiber and various matrix resin formulations. Multiple formulations of four different families of matrix resins were tested: LaRC - ITPI, LaRC - IA, RPT46T, and RP67/RP55. Report presents the materials tested and pertinent details supplied by NASA. For each material, three replicate specimens were tested. Multiple crack extensions were performed on each replicate.

Kessler, Jeff A.; Adams, Donald F.

1992-01-01

244

[Preparation and biological evaluation of PLA/chitosan composite materials].  

PubMed

Hypersusceptibility test, pyrogen test, cell cultivation, and toxicity examination were applied in the biological evaluation of the poly(lactic acid) (PLA)/chitosan composite materials. The results indicated that all the materials were negative, conforming to the ISO10993-1. The cell could grow well on the surface of the materials. So the PLA/chitosan composite materials have good biocompatibility and can be planted in the body as scaffolds. PMID:14564997

Li, Lihua; Ding, Shan; Zhou, Changren

2003-09-01

245

Composite tribological materials. (Latest citations from Fluidex). Published Search  

SciTech Connect

The bibliography contains citations concerning the properties, behavior, and uses of composite tribological materials in and on various objects, devices, and equipment. The citations examine friction and wear characteristics, mechanisms, and the performance of these materials and the objects to which they are applied. Composite tribological materials are used, for example, in bearings, gears, and piston rings. Included are self lubricating materials. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1998-02-01

246

Some functional properties of composite material based on scrap tires  

NASA Astrophysics Data System (ADS)

The utilization of scrap tires still obtains a remarkable importance from the aspect of unloading the environment from non-degradable waste [1]. One of the most prospective ways for scrap tires reuse is a production of composite materials [2] This research must be considered as a continuation of previous investigations [3, 4]. It is devoted to the clarification of some functional properties, which are considered important for the view of practical applications, of the composite material. Some functional properties of the material were investigated, for instance, the compressive stress at different extent of deformation of sample (till 67% of initial thickness) (LVS EN 826) [5] and the resistance to UV radiation (modified method based on LVS EN 14836) [6]. Experiments were realized on the purposefully selected samples. The results were evaluated in the correlation with potential changes of Shore C hardness (Shore scale, ISO 7619-1, ISO 868) [7, 8]. The results showed noticeable resistance of the composite material against the mechanical influence and ultraviolet (UV) radiation. The correlation with the composition of the material, activity of binder, definite technological parameters, and the conditions supported during the production, were determined. It was estimated that selected properties and characteristics of the material are strongly dependent from the composition and technological parameters used in production of the composite material, and from the size of rubber crumb. Obtained results show possibility to attain desirable changes in the composite material properties by changing both the composition and technological parameters of examined material.

Plesuma, Renate; Malers, Laimonis

2013-09-01

247

Vibrational damping behavior of composite materials  

NASA Astrophysics Data System (ADS)

This study was primarily undertaken to review the literature concerning damping characteristics of composites. Both theoretical and experimental investigations have substantiated that damping capacity of composites is significantly influenced by various factors including volume fraction of reinforcements, fiber aspect ratio, fiber orientation, microstructural characteristics, test temperature and frequency, applied stress, mode of vibrations, etc. Effect of these factors on loss factor of composites is briefly described in this paper.

Singh, S. S.; Rohatgi, P. K.; Keshavram, B. N.

248

Orthotic devices using lightweight composite materials  

NASA Technical Reports Server (NTRS)

Potential applications of high strength, lightweight composite technology in the orthotic field were studied. Several devices were designed and fabricated using graphite-epoxy composite technology. Devices included shoe plates, assistive walker devices, and a Simes prosthesis reinforcement. Several other projects having medical application were investigated and evaluations were made of the potential for use of composite technology. A seat assembly was fabricated using sandwich construction techniques for the Total Wheelchair Project.

Harrison, E., Jr.

1983-01-01

249

Selected NASA research in composite Materials and structures  

NASA Technical Reports Server (NTRS)

Various aspects of the application of composite materials to aircraft structures are considered. Failure prediction techniques, buckling and postbuckling research, laminate fatigue analysis, damage tolerance, high temperature resin matrix composites and electrical hazards of carbon fiber composites are among the topics discussed.

1980-01-01

250

Structural assessment of a novel carpet composite material  

NASA Astrophysics Data System (ADS)

Noise pollution caused by vehicles has always been a concern to the communities in the vicinity of highways and busy roadways. The carpet composite material was recently developed and proposed to be utilized as sound-walls in highways. In the carpet composite material post-consumer carpet is used as reinforcing element inside and epoxy matrix. The main focus of this work is to assess flexural behavior of this novel material. Tests were performed on the individual components of the composite material. Using the results from the test and a theoretical approach, a model was proposed that describes the flexural behavior and also a close estimate of the flexural strength of the carpet composite material. In this work the contribution of the carpet in flexural behavior of the composite material was investigated. It was found that the carpet is weaker than the epoxy and the contribution of the carpet in flexural strength of the composite material is small. It was also found that using the carpet inside the epoxy results in 63% decrease in ultimate strength of the section, however; the gain in ductility is considerable. Based on the flexural test results the composite section follows a bilinear behavior. To determine the capacity of the composite, the effective epoxy section is to be determined before and after the tension cracks form at the bottom of the section. Using the epoxy section analysis described in this work, the strength of the composite section can be calculated at cracking and ultimate capacity.

Abbaszadeh, Ali

251

Application of advanced material systems to composite frame elements  

NASA Technical Reports Server (NTRS)

A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

1992-01-01

252

Composite materials for precision space reflector panels  

Microsoft Academic Search

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified and thermal, mechanical and

Stephen S. Tompkins; Joan G. Funk; David E. Bowles; Timothy W. Towell; John W. Connell

1992-01-01

253

Process for fabricating composite material having high thermal conductivity  

DOEpatents

A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

Colella, Nicholas J. (Livermore, CA); Davidson, Howard L. (San Carlos, CA); Kerns, John A. (Livermore, CA); Makowiecki, Daniel M. (Livermore, CA)

2001-01-01

254

Energy absorption in composite materials for crashworthy structures  

NASA Technical Reports Server (NTRS)

Crash energy-absorption processes in composite materials have been studied as part of a research program aimed at the development of energy absorbing subfloor beams for crashworthy military helicopters. Based on extensive tests on glass/epoxy, graphite/epoxy, and Kevlar/epoxy composites, it is shown that the energy-absorption characteristics and crushing modes of composite beams are similar to those exhibited by tubular specimens of similar material and architecture. The crushing mechanisms have been determined and related to the mechanical properties of the constituent materials and specimen architecture. A simple and accurate method for predicting the energy-absorption capability of composite beams has been developed.

Farley, Gary L.

1987-01-01

255

Flexible hydrogel-based functional composite materials  

DOEpatents

A composite having a flexible hydrogel polymer formed by mixing an organic phase with an inorganic composition, the organic phase selected from the group consisting of a hydrogel monomer, a crosslinker, a radical initiator, and/or a solvent. A polymerization mixture is formed and polymerized into a desired shape and size.

2013-10-08

256

Industry technology assessment of graphite-polymide composite materials. [conferences  

NASA Technical Reports Server (NTRS)

An assessment of the current state of the art and the future prospects for graphite polyimide composite material technology is presented. Presentations and discussions given at a minisymposium of major issues on the present and future use, availability, processing, manufacturing, and testing of graphite polyimide composite materials are summarized.

1975-01-01

257

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon---carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

258

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon-carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

259

Advanced organic composite materials for aircraft structures: Future program  

NASA Technical Reports Server (NTRS)

Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

1987-01-01

260

NASA's Reusable Launch Vehicle Technologies: A Composite Materials Overview  

NASA Technical Reports Server (NTRS)

A materials overview of the NASA's Earth-to-Orbit Space Transportation Program is presented. The topics discussed are: Earth-to-Orbit Goals and Challenges; Space Transportation Program Structure; Generations of Reusable Launch Vehicles; Space Transportation Derived Requirements; X 34 Demonstrator; Fastrac Engine System; Airframe Systems; Propulsion Systems; Cryotank Structures; Advanced Materials, Fabrication, Manufacturing, & Assembly; Hot and Cooled Airframe Structures; Ceramic Matrix Composites; Ultra-High Temp Polymer Matrix Composites; Metal Matrix Composites; and PMC Lines Ducts and Valves.

Clinton, R. G., Jr.; Cook, Steve; Effinger, Mike; Smith, Dennis; Swint, Shayne

1999-01-01

261

Chromatographic behavior of silica-polymer composite molecularly imprinted materials.  

PubMed

Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based HPLC packing materials. Detailed physical and chromatographic characterization of such a silica-MIP composite material is presented. The chromatographic peak shape obtained with the uniformly sized spherical silica-MIP composite is mainly determined by the nonlinear adsorption isotherm. Comparison of the composite with the conventional sieved and grinded bulk MIP is therefore based on the nonlinear isotherm and not on retention factors and plate numbers. PMID:16188268

Tth, B; Lszl, K; Horvai, G

2005-12-23

262

Development of novel polymer\\/quasicrystal composite materials  

Microsoft Academic Search

We report on a new class of materials, polymer\\/quasicrystal composites with useful properties for beneficial exploitation in applications, such as dry bearings and composite gears. Our preliminary results indicate that our new composites are a means of enhancing the properties of certain organic polymers while providing a new means of processing quasicrystals. AlCuFe quasicrystalline materials significantly improved wear resistance to

Paul D Bloom; K. G Baikerikar; Joshua U Otaigbe; Valerie V Sheares

2000-01-01

263

Pressure variation assisted fiber extraction and development of high performance natural fiber composites and nanocomposites  

NASA Astrophysics Data System (ADS)

It is believed, that due to the large surface areas provided by the nano scale materials, various composite properties could be enhanced when such particles are incorporated into a polymer matrix. There is also a trend of utilizing natural resources or reusing and recycling materials that are already available for the fabrication of the new composite materials. Cellulose is the most abundant natural polymer on the planet, and therefore it is not surprising to be of interest for composite fabrication. Basic structures of cellulose, comprised of long polysaccharide chains, are the building blocks of cellulose nano fibers. Nano fibers are further bound into micro fibrils and macro fibers. Theoretically pure cellulose nano fibers have tremendous strengths, and therefore are some of the most sought after nano particles. The fiber extraction however is a complex task. The ultrasound, which creates pressure variation in the medium, was employed to extract nano-size cellulose particles from microcrystalline cellulose (MCC). The length and the intensity of the cavitations were evaluated. Electron microscopy studies revealed that cellulose nanoparticles were successfully obtained from the MCC after ultrasound treatment of just 30 minutes. Structure of the fractionated cellulose was also analyzed with the help of X-ray diffraction, and its thermal properties were evaluated with the help of differential scanning calorimetry (DSC). Ultrasound treatment performed on the wheat straw, kenaf, and miscanthus particles altered fiber structure as a result of the cavitation. The micro fibers were generated from these materials after they were subjected to NaOH treatment followed by the ultrasound processing. The potential of larger than nano-sized natural fibers to be used for composite fabrication was also explored. The agricultural byproducts, such as wheat or rice straw, as well as other fast growing crops as miscanthus or kenaf, are comprised of three basic polymers. Just like in wood the polymers are: cellulose, hemicelluloses, and lignin. When subjected to elevated pressures and temperatures, we are able to get access to some of these natural polymers and use them as a matrix material for composite fabrication. Therefore, fabrication of composite materials without addition of synthetic polymers is possible. Thermal and mechanical properties of such composites are evaluated with the help of electron microscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and flexural strength measurements. The chemical changes in the composites are also probed with the help of Fourier transform infrared (FTIR) analysis. Various additives introduced into composite materials provide different properties. The addition of small amounts of synthetic polymers further enhances the properties of natural fiber composites and do not require high fabrication pressures. Calcium sulfite crystals, which are one of the coal combustion products, were combined with the natural fibers and recycled HDPE polymer to form wood substitute composites. The introduction of these additives resulted in composites with the properties similar to those of the natural wood. Coal combustion products, often used in composite material fabrication, contain mercury which may be rereleased during composite fabrication. Mercury behavior under composite fabrication conditions, such as elevated pressures and temperatures were evaluated. Sulfite rich scrubber material, generated during the flue gas desulphurization process was the main target of the study. It was observed that the release of the mercury is highly dependent on the composite fabrication pressure as well as the temperature.

Markevicius, Gediminas

264

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...

2009-04-01

265

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...

2010-04-01

266

Study of composites as substrate materials in large space telescopes  

NASA Technical Reports Server (NTRS)

Nonmetallic composites such as the graphite/epoxy system were investigated as possible substrates for the primary mirror of the large space telescope. The possible use of fiber reinforced metal matrix composites was reviewed in the literature. Problems arising out of the use of composites as substrate materials such as grinding, polishing, adherence of reflective coatings, rigidity of substrate, hygrospcopici tendency of the composites, thermal and temporal stability and other related problems were examined.

Sharma, A. V.

1979-01-01

267

Corrosion inhibiting composition for treating asbestos containing materials  

DOEpatents

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed, wherein the composition comprises water, at least about 30% by weight of an acid component, optionally a source of fluoride ions, and a corrosion inhibiting amount of thiourea, a lower alkylthiourea, a C.sub.8 -C.sub.15 alkylpyridinium halide or mixtures thereof. A method of transforming an asbestos-containing building material, while part of a building structure, into a non-asbestos material by using the present composition also is disclosed.

Hartman, Judithann Ruth (Columbia, MD) [Columbia, MD

1998-04-21

268

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

A layered planar structure consisting of different bianisotropic materials separated by jump-immittance sheets is considered. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Applications are important for radomes and radar-absorbing materials.

Graglia, Roberto D.; Uslenghi, Piergiorgio L. E.

1991-01-01

269

Composite material application for liquid rocket engines  

NASA Technical Reports Server (NTRS)

With increasing emphasis on improving engine thrust-to-weight ratios to provide improved payload capabilities, weight reductions achievable by the use of composites have become attractive. Of primary significance is the weight reduction offered by composites, although high temperature properties and cost reduction were also considered. The potential for application of composites to components of Earth-to-orbit hydrocarbon engines and orbit-to-orbit LOX/H2 engines was assessed. The components most likely to benefit from the application of composites were identified, as were the critical technology areas where developed would be required. Recommendations were made and a program outlined for the design, fabrication, and demonstration of specific engine components.

Heubner, S. W.

1982-01-01

270

Antifouling Glass-Reinforced Composite Materials.  

National Technical Information Service (NTIS)

Various organometallic polyesters and epoxies were prepared by different synthetic methods. These novel plastics will be used to prepare antifouling glass-reinforced composites for marine structural applications such as use in seawater piping systems. An ...

J. A. Montemarano S. A. Cohen

1976-01-01

271

Stress Wave Propagation in Hybrid Composite Materials.  

National Technical Information Service (NTIS)

The dynamic response, in particular, the interlaminar shear stress, in three layer symmetrical hybrid composites is studied using the shear lag model. Theoretical solutions for four different types of loading are obtained. Numerical examples are given for...

Y. L. Li C. Ruiz J. Harding

1990-01-01

272

Wear resistance of composite materials. (Latest citations from Engineered Materials abstracts). Published Search  

SciTech Connect

The bibliography contains citations concerning wear resistance of composite materials. References discuss polymer, ceramic and metal composites. Tribological testing and failure analyses are included. (Contains a minimum of 200 citations and includes a subject term index and title list.)

Not Available

1994-09-01

273

Leaching of technologically enhanced naturally occurring radioactive materials.  

PubMed

A form of waste associated with mining activities is related to the type of deposit being mined and to the procedure of exploitation and enrichment adopted. The wastes usually contain relatively large amounts of technologically enhanced naturally occurring radioactive materials (TENORM). The TENORM are often stored on the surface. Consequently, they can be leached as a result of interaction with aqueous solutions of different chemical composition. This further leads to pollution of water and soil in the vicinity of the stored wastes. The paper presents the results of laboratory investigation aimed at quantifying the leaching process of samples originating from uranium dumps and storage reservoirs associated with brine pumped from coal mines. The leaching process was investigated with respect to selected elements: uranium isotopes, radium isotopes, iron, barium and sodium. The samples were exposed to aqueous solutions of different chemical composition. The experiments revealed that TENORM in form of sulphate compounds are the most resistant against leaching. The leaching coefficient for radium isotopes varies from a few thousandth percent to a few hundredth percent. On the other hand, for TENORM occurring in sand or sludge, the leaching coefficient for uranium and radium isotopes ranged from a few hundredth percent to a few percent. PMID:17482828

Chau, Nguyen Dinh; Chru?ciel, Edward

2007-08-01

274

Multilayer composite material and method for evaporative cooling  

NASA Technical Reports Server (NTRS)

A multilayer composite material and method for evaporative cooling of a person employs an evaporative cooling liquid that changes phase from a liquid to a gaseous state to absorb thermal energy. The evaporative cooling liquid is absorbed into a superabsorbent material enclosed within the multilayer composite material. The multilayer composite material has a high percentage of the evaporative cooling liquid in the matrix. The cooling effect can be sustained for an extended period of time because of the high percentage of phase change liquid that can be absorbed into the superabsorbent. Such a composite can be used for cooling febrile patients by evaporative cooling as the evaporative cooling liquid in the matrix changes from a liquid to a gaseous state to absorb thermal energy. The composite can be made with a perforated barrier material around the outside to regulate the evaporation rate of the phase change liquid. Alternatively, the composite can be made with an imperveous barrier material or semipermeable membrane on one side to prevent the liquid from contacting the person's skin. The evaporative cooling liquid in the matrix can be recharged by soaking the material in the liquid. The multilayer composite material can be fashioned into blankets, garments and other articles.

Buckley, Theresa M. (Inventor)

2002-01-01

275

Resin-based composite as a direct esthetic restorative material.  

PubMed

The search for an ideal esthetic material for tooth restoration has resulted in significant improvements in both materials and the techniques for using them. Various resin-based composite (RBC) materials have recently been introduced into the market that offer improved esthetic and physical properties. This article reviews RBCs, including their compositions, advantages, and disadvantages, that are contemporary to today's clinical practice as well as those that are under research consideration and/ or in clinical trial phase. PMID:21755892

Malhotra, Neeraj; Mala, Kundabala; Acharya, Shashirashmi

2011-06-01

276

Development of some bio-composite materials hydroxyapatite\\/chitosan and TiO2\\/chitosan  

Microsoft Academic Search

New-type materials, which consist of organic and inorganic compounds, have been prepared. The materials have various functions and specific nature because of their improved mechanical, thermal, optical, or chemical properties relative to the organic or inorganic materials alone. The aim of this study is to prepare and characterise micro composite films hydroxyapatite\\/chitosane and TiO2\\/chitosane of which the use could be

S. Essakali; A. Kheribech; M. Bakasse; Z. Hatim

2008-01-01

277

Flexible composite material with phase change thermal storage  

NASA Technical Reports Server (NTRS)

A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, ,gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

2001-01-01

278

Deformation and failure information from composite materials via acoustic emission  

NASA Technical Reports Server (NTRS)

The paper reviews some principles of applying acoustic emission (AE) to the study of fiber-composite materials and structures. This review covers the basics of using AE to monitor the deformation and fracture processes that occur when fiber-composite materials are stressed. Also, new results in some areas of current research interest are presented. The following areas are emphasized: study of couplants for AE testing of composites, evaluation of a special immersion-type AE transducer, and wave propagation complications and the development of techniques for locating AE sources in Kevlar 49/epoxy composite pre

Hamstad, M. A.

1978-01-01

279

Composite-Material Tanks with Chemically Resistant Liners  

NASA Technical Reports Server (NTRS)

Lightweight composite-material tanks with chemically resistant liners have been developed for storage of chemically reactive and/or unstable fluids . especially hydrogen peroxide. These tanks are similar, in some respects, to the ones described in gLightweight Composite-Material Tanks for Cryogenic Liquids h (MFS-31379), NASA Tech Briefs, Vol. 25, No. 1 (January, 2001), page 58; however, the present tanks are fabricated by a different procedure and they do not incorporate insulation that would be needed to prevent boil-off of cryogenic fluids. The manufacture of a tank of this type begins with the fabrication of a reusable multisegmented aluminum mandrel in the shape and size of the desired interior volume. One or more segments of the mandrel can be aluminum bosses that will be incorporated into the tank as end fittings. The mandrel is coated with a mold-release material. The mandrel is then heated to a temperature of about 400 F (approximately equal to 200 C) and coated with a thermoplastic liner material to the desired thickness [typically approxiamtely equal to 15 mils (approximately equal to 0.38 mm)] by thermal spraying. In the thermal-spraying process, the liner material in powder form is sprayed and heated to the melting temperature by a propane torch and the molten particles land on the mandrel. The sprayed liner and mandrel are allowed to cool, then the outer surface of the liner is chemically and/or mechanically etched to enhance bonding of a composite overwrap. The etched liner is wrapped with multiple layers of an epoxy resin reinforced with graphite fibers; the wrapping can be done either by manual application of epoxy-impregnated graphite cloth or by winding of epoxy-impregnated filaments. The entire assembly is heated in an autoclave to cure the epoxy. After the curing process, the multisegmented mandrel is disassembled and removed from inside, leaving the finished tank. If the tank is to be used for storing hydrogen peroxide, then the liner material should be fluorinated ethylene/propylene (FEP), and one or more FEP O ring(s) should be used in the aluminum end fitting(s). This choice of materials is dictated by experimental observations that pure aluminum and FEP are the only materials suitable for long-term storage of hydrogen peroxide and that other materials tend to catalyze the decomposition of hydrogen peroxide to oxygen and water. Other thermoplastic liner materials that are suitable for some applications include nylon 6 and polyethylene. The processing temperatures for nylon 6 are lower than those for FEP. Nylon 6 is compatible with propane, natural gas, and other petroleum-based fuels. Polyethylene is compatible with petroleum- based products and can be used for short-term storage of hydrogen peroxide.

DeLay, Thomas K.

2004-01-01

280

Glass flake reinforced composites as optical materials.  

PubMed

The optical properties of glass flake composites are investigated by measuring the transmission of collections of flakes in index matched oils over a wide temperature range. For large refractive index differences between glass and matrix, the transmission is periodic with temperature and is interpreted as Fresnel diffraction from a transparent edge. For small refractive index differences, the Rayleigh-Gans (RG) light scattering theory for thin circular disks is used to correlate the data. A model is developed for predicting the flake size and concentration necessary in a particular polymer matrix for the resulting composite to meet given temperature dependent haze requirements. PMID:20700346

Dunlap, P N

1991-05-01

281

Glass flake reinforced composites as optical materials  

NASA Astrophysics Data System (ADS)

The optical properties of glass flake composites are investigated by measuring the transmission of collections of flakes in index matched oils over a wide temperature range. For large refractive index differences between glass and matrix, the transmission is periodic with temperature and is interpreted as Fresnel diffraction from a transparent edge. For small refractive index differences, the Rayleigh-Gans (RG) light scattering theory for thin circular disks is used to correlate the data. A model is developed for predicting the flake size and concentration necessary in a particular polymer matrix for the resulting composite to meet given temperature dependent haze requirements.

Dunlap, Paul N.

1991-05-01

282

Material, process, and product design of thermoplastic composite materials  

Microsoft Academic Search

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP\\/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength

Heming Dai

2001-01-01

283

Natural Cellulosic Substance Derived Nano-structured Materials  

Microsoft Academic Search

\\u000a When versatile synthetic chemical processes meet natural biological assemblies, a promising shortcut for the design and fabrication\\u000a of functional materials with tailored structures and properties are lit up. By precisely replicating natural substrates with\\u000a guest matrices, artificial materials are endowed with the initial biological structures and morphologies. To achieve faithful\\u000a inorganic\\/organic replicas of the natural species for the corresponding finest

Yuanqing Gu; Jianguo Huang

284

Cost of Automotive Polymer Composites: A Review and Assessment of DOE's Lightweight Materials Composites Research.  

National Technical Information Service (NTIS)

Polymer composite materials have been a part of the automotive industry for several decades but economic and technical barriers have constrained their use. To date, these materials have been used for applications with low production volumes because of the...

S. Das

2001-01-01

285

A Composite Material in the Al B C System  

Microsoft Academic Search

Results of a study of a material prepared by impregnating boron carbide with aluminum are reported. A shortcoming of this composite material is that it tends to degrade (at a different rate depending on the conditions) into a powder. Introduction of boron and magnesium diboride enhances the material stability; however, specimens high in aluminum carbide are the most prone to

V. S. Neshpor; G. P. Zaitsev; S. V. Zhuravlev; A. A. Kitsai; M. A. Aizenberg; V. A. Pesin

2003-01-01

286

Left-handed materials in metallic magnetic granular composites  

Microsoft Academic Search

There is recently interests in the left-handed materials. In these materials the direction of the wave vector of electromagnetic radiation is opposite to the direction of the energy flow. We present simple arguments that suggests that magnetic composites can also be left-handed materials. However, the physics involved seems to be different from the original argument. In our argument, the imaginary

S. T. Chui; Z. F. Lin; L.-B. Hu

2003-01-01

287

Carbon Cryogel Silicon Composite Anode Materials for Lithium Ion Batteries.  

National Technical Information Service (NTIS)

A variety of materials are under investigation for use as anode materials in lithium-ion batteries, of which, the most promising are those containing silicon. 10 One such material is a composite formed via the dispersion of silicon in a resorcinol-formald...

R. Baldwin W. Bennett

2010-01-01

288

Effect of particle size in composite materials on radiative properties  

NASA Technical Reports Server (NTRS)

A numerical model for the radiative properties of a composite material composed of ceramic oxide fibers and particles was developed and used to determine the effect of the size parameters of the two components. Results include the computed phase functions for the zirconia and silica composite materials, showing the location and strength of the strong forward-scattering peak. The phase function and the optical properties of the composite are strongly influenced by the particle size parameter through the fiber or particle diameter and the wavelength, the material, and the mixture fraction.

Lee, Siu-Chun; White, Susan; Grzesik, Jan

1993-01-01

289

Preparation of composite materials in space. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

A study to define promising materials, significant processing criteria, and the related processing techniques and apparatus for the preparation of composite materials in space was conducted. The study also established a program for zero gravity experiments and the required developmental efforts. The following composite types were considered: (1) metal-base fiber and particle composites, including cemented compacts, (2) controlled density metals, comprising plain and reinforced metal foams, and (3) unidirectionally solidified eutectic alloys. A program of suborbital and orbital experiments for the 1972 to 1978 time period was established to identify materials, processes, and required experiment equipment.

Steurer, W. H.; Kaye, S.

1973-01-01

290

Field-responsive smart composite particle suspension: materials and rheology  

NASA Astrophysics Data System (ADS)

Both electrorheological (ER) and magnetorheological (MR) fluids are known to be smart materials which can be rapidly and reversibly transformed from a fluid-like to a solid-like state within milliseconds by showing dramatic and tunable changes in their rheological properties under external electrical or magnetic field strength, respectively. Here, among various smart composite particles studied, recently developed core-shell structured polystyrene/graphene oxide composite based ER material as well as the dual-step functionally coated carbonyl iron composite based MR material are briefly reviewed along with their rheological characteristics under external fields.

Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin

2012-09-01

291

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

292

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. he sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaC12,...

293

Advanced AE Techniques in Composite Materials Research  

NASA Technical Reports Server (NTRS)

Advanced, waveform based acoustic emission (AE) techniques have been successfully used to evaluate damage mechanisms in laboratory testing of composite coupons. An example is presented in which the initiation of transverse matrix cracking was monitored. In these tests, broad band, high fidelity acoustic sensors were used to detect signals which were then digitized and stored for analysis. Analysis techniques were based on plate mode wave propagation characteristics. This approach, more recently referred to as Modal AE, provides an enhanced capability to discriminate and eliminate noise signals from those generated by damage mechanisms. This technique also allows much more precise source location than conventional, threshold crossing arrival time determination techniques. To apply Modal AE concepts to the interpretation of AE on larger composite specimens or structures, the effects of modal wave propagation over larger distances and through structural complexities must be well characterized and understood. To demonstrate these effects, measurements of the far field, peak amplitude attenuation of the extensional and flexural plate mode components of broad band simulated AE signals in large composite panels are discussed. These measurements demonstrated that the flexural mode attenuation is dominated by dispersion effects. Thus, it is significantly affected by the thickness of the composite plate. Furthermore, the flexural mode attenuation can be significantly larger than that of the extensional mode even though its peak amplitude consists of much lower frequency components.

Prosser, William H.

1996-01-01

294

The Thermal Properties of Composite Materials.  

National Technical Information Service (NTIS)

The thermal expansion behaviour of composites consisting of copper spheres in epoxy and glass ballotini in epoxy has been investigated from 77 K up to about 450 K using a capacitative technique. The effect of the size of the particles on the thermal expan...

H. M. Rosenberg

1978-01-01

295

Composite materials reinforced with polyoxymethylene whiskers  

Microsoft Academic Search

Various composite samples reinforced with polyoxymethylene (POM) whisker crystals were prepared and their Young's moduli were measured and analysed, on a theoretical equation, to estimate the modulus of the filler itself. Good reinforcement was obtained with matrix resins such as an epoxide and an unsaturated polyester, the results giving the modulus of the whisker to be approximately 11011 N m-2,

M. Iguchi; T. Suehiro; Y. Watanabe; Y. Nishi; M. Uryu

1982-01-01

296

Fundamentals of Interfacial Strength in Composite Materials.  

National Technical Information Service (NTIS)

The current research period has emphasized 6061 and 7090 aluminum alloys as composite matrices, both with particulates SiC reinforcements. As in our previous work, we have found the fracture behavior to be sensitive to both process variables (in this case...

A. Voelkel A. W. Thompson I. M. Bernstein

1987-01-01

297

Composite materials: Fatigue and fracture (sixth volume)  

SciTech Connect

The symposium featured presentations covering metal matrix composites, fatigue, and damage progression, strength and residual properties, damage tolerance and fracture analysis, mode mixity and delamination, property characterization and environmental effects, and standardization and design. Separate abstracts were prepared for most papers in this volume.

Armanios, E.A. [ed.

1997-12-31

298

Dynamics of Cracked Composite Material Structures.  

National Technical Information Service (NTIS)

As a result of this work models of the finite beam and plate elements have been elaborated, to enable the analysis of the influence of the fatigue cracks and delaminations on the dynamic characteristics of the constructions made of unidirectional composit...

W. M. Ostachowicz M. Krawczuk A. Zak

1995-01-01

299

LIGNOCELLULOSIC-PLASTIC COMPOSITES FROM RECYCLED MATERIALS  

EPA Science Inventory

Waste wood, waste paper, and waste plastics are major components of MSW and offer great opportunities as recycled ingredients in wood-fiber plastic composites. USEPA and the USDA Forest Products Laboratory (FPL) are collaborating on a research project to investigate the processin...

300

Comparison of self repair in various composite matrix materials  

NASA Astrophysics Data System (ADS)

In a comparison of self repair in graphite composites (for airplane applications) versus epoxy and vinyl ester composites (for building structures or walls) 1 the type of damage that the fiber/matrix is prone to experience is a prime factor in determining which materials self repair well and 2 the flow of energy during damage determines what kinds of damage that can be self repaired well. 1) In brittle composites, repair was successful throughout the composite due to matrix cracking which allowed for optimum chemical flow, whereas in toughened composites that did not crack, the repair chemical flows into a few layers of the composite. 2) If the damage energy is stopped by the composite and goes laterally, it causes delamination which will be repaired; however if the damage energy goes through the composite as with a puncture, then there will be limited delamination, less chemical release and less self repair.

Dry, Carolyn

2014-04-01

301

Natural and technologic hazardous material releases during and after natural disasters: a review  

Microsoft Academic Search

Natural disasters may be powerful and prominent mechanisms of direct and indirect hazardous material (hazmat) releases. Hazardous materials that are released as the result of a technologic malfunction precipitated by a natural event are referred to as natural-technologic or na-tech events. Na-tech events pose unique environmental and human hazards. Disaster-associated hazardous material releases are of concern, given increases in population

Stacy Young; Lina Balluz; Josephine Malilay

2004-01-01

302

High temperature composite materials and magnetodielectric composites for microwave application  

NASA Astrophysics Data System (ADS)

In the part I, we investigated the microstructures, mechanical properties, and oxidation behavior of hot pressed BN in the presence of sintering additives Al2O3, Y2O3 and SiO2. BN platelets size in the sintered samples grew from 5 to 30 times for the use of all three oxides, and the use of Al2O3 and Y2O3, correspondingly. The excessive growth of BN platelets in samples containing Al2O3 and Y2O 3 caused them to misalign which, in turn, resulted in its low relative density (92.0%). The use of SiO2 mitigated this grain growth so that BN platelets aligned better to gain a higher relative density (99.5%). Flexural strength and elastic modulus of BN were proportional to their densities. Oxidation experiments conducted at 1200C in flowing dry air showed borate glass droplets were formed on all of oxidized BN samples. The addition of SiO2 resulted in the formation of a glass layer before the appearance of these glass droplets. The presence of glass droplets was a result of the poor wetting of liquid B2O3 on BN and the dominance of the formation of B2O3 to its evaporation. Their size evolution described the "breadth figure" theory, similar to the formation of water droplets on a flat surface from the saturated water vapor air. Substructures observed inside the glass droplets contained high and consistent Al:Y atomic ratio (5:7) in all samples. The evaporation of B2O 3 isolated Al2O3, Y2O3 in the form of immiscible liquid phase to borate. In the part II, we investigated the formulation of equivalent permittivity and permeability with isotropic and anisotropic Co2Z-polymer composition. These two properties of isotropic Co2Z-LDPE/Co2Z-Silicone composites increased with Co2Z composition. However, their permittivity was always higher than that of their permeability. Permittivity and permeability of anisotropic Co2Z-Silicone composites were split into high and low values along the parallel and perpendicular directions to the alignment direction of Co2Z particles. The separation at 20 vol% Co2Z was strongest, attained 46% anisotropy so that its parallel permeability approached closer to that of its perpendicular permittivity. However, the low permittivity of Co2Z required a higher electric field to increase its particles' alignment.

Do, Thanh Ba

303

Naturally occurring radioactive materials and medical isotopes at border crossings  

Microsoft Academic Search

Countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders. Some cargo contains naturally occurring radioactive material (NORM) or technologically enhanced NORM (TENORM) that triggers alarms at border crossings. This paper discusses experience with radiation portal monitors for the interdiction of radioactive materials and the issues raised by NORM. The

R. T. Kouzes; J. H. Ely; B. D. Geelhood; R. R. Hansen; E. A. Lepel; J. E. Schweppe; L. Siciliano; R. A. Warner

2003-01-01

304

Electrical Characterizations of Lightning Strike Protection Techniques for Composite Materials  

NASA Technical Reports Server (NTRS)

The growing application of composite materials in commercial aircraft manufacturing has significantly increased the risk of aircraft damage from lightning strikes. Composite aircraft designs require new mitigation strategies and engineering practices to maintain the same level of safety and protection as achieved by conductive aluminum skinned aircraft. Researchers working under the NASA Aviation Safety Program s Integrated Vehicle Health Management (IVHM) Project are investigating lightning damage on composite materials to support the development of new mitigation, diagnosis & prognosis techniques to overcome the increased challenges associated with lightning protection on composite aircraft. This paper provides an overview of the electrical characterizations being performed to support IVHM lightning damage diagnosis research on composite materials at the NASA Langley Research Center.

Szatkowski, George N.; Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Mielnik, John J.

2009-01-01

305

Additive Composition for Making Dental Materials.  

National Technical Information Service (NTIS)

The patent application relates to a substitute for distilled water normally used in the fabrication or preparation of dental materials. The addition of ammonium stabilized colloidal silica, borax and boric acid to the distilled water in which dental porce...

C. P. Mabie

1976-01-01

306

Metal oxide composite dosimeter method and material  

DOEpatents

The present invention is a method of measuring a radiation dose wherein a radiation responsive material consisting essentially of metal oxide is first exposed to ionizing radiation. The metal oxide is then stimulating with light thereby causing the radiation responsive material to photoluminesce. Photons emitted from the metal oxide as a result of photoluminescence may be counted to provide a measure of the ionizing radiation.

Miller, Steven D. (Richland, WA)

1998-01-01

307

Casting of superconducting composite materials (M-4)  

NASA Technical Reports Server (NTRS)

An aluminum-lead-bismuth alloy is a flexible alloy and is promising for easily workable embedded-type, filament-dispersed superconducting wire material. It is difficult to produce homogeneous ingots of this material because it is easily separated into elements when melted on Earth due to the large specific gravity differences. In this experiment, a homogeneous alloy will first be produced in molten state in microgravity. It will then be returned to Earth and processed into a wire or tape form. It will then be dispersed as the second phase in micro texture form into the primary phase of aluminum. Superconducting wire material with high-critical-magnetic-field characteristics will be produced. The texture of the material will be observed, and its performance will be evaluated. In addition to the above alloy, a four-element alloy will be produced from silver, a rare Earth element, barium, and copper. The alloys will be oxidized and drawn into wire after being returned to Earth. The materials are expected to be forerunners in obtaining superconducting wire materials from oxide superconductors.

Togano, Kazumasa

1993-01-01

308

Investigating Tungsten Concentrations and Isotopic Compositions of Natural Water Samples from the Carson River Basin  

NASA Astrophysics Data System (ADS)

Recent studies have shown that W-isotopes may fractionate in nature1; however, the magnitude and cause of the isotopic variations are largely unknown and unconstrained. In this study, the isotopic compositions of the NIST 3163 W standard, W ore minerals, and 15 natural surface waters from Nevada's Carson River Basin were analyzed by MC-ICP-MS using external bracketing with NIST 3163 and the IUPAC 184W/183W for mass bias correction. Chemical separation procedures were developed to purify W from natural matrices and tested to assure fractionation was not introduced during column chemistry. The W isotopic compositions of these samples were measured and compared to the accepted IUPAC composition of natural W. Samples of wolframite (Fe, MnWO4) and hubnerite (MnWO4) have compositions similar to the IUPAC value but vary from the isotopic composition of NIST 3163 - particularly in 182W/183W. The isotopic compositions of the natural waters, except for an extremely evaporated sample from Soda Lake, are similar to the NIST standard. This evaporative lake, formed by a maar, has a unique chemical composition compared to other surface waters with high W (800 20 ng/g) and As (1665 17 ng/g) concentrations; and relatively low Fe (5.00 0.13 ng/g) and Mn (0.52 0.07 ng/g). These results support recent observations of natural W isotopic variation and imply that W-isotope compositions may be useful for environmental applications of stable isotope geochemistry. 1. Irisawa, K. and Hirata, T. (2006) Tungsten isotopic analysis on six geochemical reference materials using multiple collector-ICP-mass spectrometry coupled with a rhenium-external correction technique. Journal of Analytical Atomic Spectrometry 21, 1387-1395.

Wasserman, N. L.; Williams, R. W.; Kayzar, T. M.; Schorzman, K. C.

2012-12-01

309

Holographic imaging of natural-fiber-containing materials  

DOEpatents

The present invention includes methods and apparatuses for imaging material properties in natural-fiber-containing materials. In particular, the images can provide quantified measures of localized moisture content. Embodiments of the invention utilize an array of antennas and at least one transceiver to collect amplitude and phase data from radiation interacting with the natural-fiber-containing materials. The antennas and the transceivers are configured to transmit and receive electromagnetic radiation at one or more frequencies, which are between 50 MHz and 1 THz. A conveyance system passes the natural-fiber-containing materials through a field of view of the array of antennas. A computing device is configured to apply a synthetic imaging algorithm to construct a three-dimensional image of the natural-fiber-containing materials that provides a quantified measure of localized moisture content. The image and the quantified measure are both based on the amplitude data, the phase data, or both.

Bunch, Kyle J. (Richland, WA) [Richland, WA; Tucker, Brian J. (Pasco, WA) [Pasco, WA; Severtsen, Ronald H. (Richland, WA) [Richland, WA; Hall, Thomas E. (Kennewick, WA) [Kennewick, WA; McMakin, Douglas L. (Richland, WA) [Richland, WA; Lechelt, Wayne M. (West Richland, WA) [West Richland, WA; Griffin, Jeffrey W. (Kennewick, WA) [Kennewick, WA; Sheen, David M. (Richland, WA) [Richland, WA

2010-12-21

310

Flight service environmental effects on composite materials and structures  

NASA Technical Reports Server (NTRS)

NASA Langley and the U.S. Army have jointly sponsored programs to assess the effects of realistic flight environments and ground-based exposure on advanced composite materials and structures. Composite secondary structural components were initially installed on commercial transport aircraft in 1973; secondary and primary structural components were installed on commercial helicopters in 1979; and primary structural components were installed on commercial aircraft in the mid-to-late 1980's. Service performance, maintenance characteristics, and residual strength of numerous components are reported. In addition to data on flight components, 10 year ground exposure test results on material coupons are reported. Comparison between ground and flight environmental effects for several composite material systems are also presented. Test results indicate excellent in-service performance with the composite components during the 15 year period. Good correlation between ground-based material performance and operational structural performance has been achieved.

Dexter, H. Benson; Baker, Donald J.

1992-01-01

311

Transient Response of Laminated, Bimodular-Material, Composite Rectangular Plates.  

National Technical Information Service (NTIS)

Finite-element and closed-form solutions to the equations of motion governing layered composite plates of bimodular materials are presented for rectangular plates with all edges simply supported without in-plane restraint and tangential rotation and subje...

J. N. Reddy

1981-01-01

312

Properties of Composite Materials for Use in Expedient Paving Systems.  

National Technical Information Service (NTIS)

Uniaxial flexure and tension tests and biaxial flexure tests were performed on two systems of fiberglass reinforced polyester (FRP) and also on a FRP-polyurethane foam composite to evaluate their suitability for possible use as expedient paving materials....

L. H. Irwin W. A. Dunlap

1974-01-01

313

Nondestructive testing of polymer composite materials using THz radiation  

NASA Astrophysics Data System (ADS)

This paper shows an ability to find internal defects in construction of polymer composite material using THz imaging. Using THz vision system resulted in an example of finding internal non-impregnated area in fiberglass.

Yakovlev, Egor V.; Zaytsev, Kirill I.; Fokina, Irina N.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

2014-03-01

314

Space radiation effects on composite matrix materials - Analytical approaches  

NASA Technical Reports Server (NTRS)

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.

1979-01-01

315

A broadband magneto-electric transducer using a composite material  

Microsoft Academic Search

This article deals with the application of a composite material as a magneto-electric transducer. The composite, which has both magneto-strictive and piezo-electric properties was developed at Philips' Research Laboratories. A transducer consisting of a piece of composite appears to be a suitable replacement for e.g. Hall devices, especially in AC applications. It needs only two electrical contacts and has a

L. P. M. BRACKE; R. G. VAN VLIET

1981-01-01

316

Electromagnetic Properties of a New Ferrite-Ceramic Composite Material  

Microsoft Academic Search

NiCuZn ferrite-CaCu3Ti4O12 composite materials which possess both capacitive and inductive properties for suppressing electromagnetic interference (EMI) were synthesized by a solid-state reaction. As the CaCu3Ti4O12 content increases from 1 to 30 wt%, the epsiv' of the composites measured at 100 Hz increases from 35 to 12 000 while the mu' of the composites measured at 100 kHz decreases from 1800

Ying He; Huaiwu Zhang; Weiwei Ling; Chunhong Mu; Yuanxun Li; Jian Shen

2009-01-01

317

Semiempirical analysis of materials' elemental composition to formulate tissue-equivalent materials: a preliminary study  

NASA Astrophysics Data System (ADS)

Tissue-equivalent materials are used for simplifying quality control and quality assurance procedures, both in diagnostic and therapeutic radiology. Important information to formulate a tissue-equivalent material is elemental composition of its base materials. However, this information is not easily obtained. Therefore we propose a stoichiometric analysis method to investigate the elemental composition of the base materials that can potentially be used for manufacturing tissue-equivalent materials. In this technique, we combined the stoichiometric calibration and the basic data method to obtain the elemental composition of materials from measured computer tomography (CT) numbers. The elemental composition, with the maximum number of the elements of the material in question up to the available number of different tube voltages at the CT scanner, was analysed using the proposed approach. We tested eight different cylinders in this study. The estimated elemental compositions of unspecified materials in the cylinders were evaluated by comparing the calculated and the simulated CT numbers to the measured ones; the results showed good correlation with maximum absolute differences of 1.9 and 3.7 HU, respectively. The accuracy of the stoichiometric analysis method to estimate the elemental composition was influenced by the accuracy of the measured CT numbers. The method proposed allows for determining the elemental composition of the base materials which can then be applied further to formulate tissue-equivalent materials.

Yohannes, Indra; Kolditz, Daniel; Kalender, Willi A.

2011-05-01

318

Electrodeposition of composites: an expanding subject in electrochemical materials science  

Microsoft Academic Search

Recent literature on composite electrodeposition is reviewed, with special attention to new application fields which are being developed, besides the well-established coating preparation. It is shown how alternative matrix materials, like conducting polymers, oxides and salts, have been investigated in order to produce composites with properties appropriate to their use in electrocatalysis, fabrication of photoactive devices and energy storage.

Marco Musiani

2000-01-01

319

Iatrogenic tooth abrasion comparisons among composite materials and finishing techniques  

Microsoft Academic Search

Statement of Problem. Many different rotary instruments are available for shaping composite restorations. Whether use of these instruments causes undesirable iatrogenic abrasion of either the tooth surface or the composite restorative material is unknown. Assuming that damage occurs, which technique is least damaging is unknown. Purpose. This in vitro study quantified the loss of surface enamel and dentin surrounding Class

Christina A. Mitchell; Maria R. Pintado; William H. Douglas

2002-01-01

320

Generating Finite-Element Models Of Composite Materials  

NASA Technical Reports Server (NTRS)

Program starts at micromechanical level, from simple inputs supplied by user. COMGEN, COmposite Model GENerator, is interactive FORTRAN program used to create wide variety of finite-element models of continuous-fiber composite materials at micromechanical level. Quickly generates batch or "session files" to be submitted to finite-element preprocessor and postprocessor program, PATRAN. COMGEN requires PATRAN to complete model.

Melis, M. E.

1993-01-01

321

In situ Strain and Temperature Monitoring of Adaptive Composite Materials  

Microsoft Academic Search

An optical fiber sensor is designed to simultaneously measure strain and temperature in an adaptive composite material. The sensor is formed by splicing two fiber Bragg gratings (FBGs) close to each other, which are written in optical fibers with different core dopants and concentrations. Their temperature sensitivities are hence different. The sensor is tested on an adaptive composite laminate made

Hyuk-Jin Yoon; Daniele Marco Costantini; Hans Georg Limberger; Ren Paul Salath; Chun-Gon Kim; Veronique Michaud

2006-01-01

322

Joining and fabrication of metal-matrix composite materials  

NASA Technical Reports Server (NTRS)

Manufacturing technology associated with developing fabrication processes to incorporate metal-matrix composites into flight hardware is studied. The joining of composite to itself and to titanium by innovative brazing, diffusion bonding, and adhesive bonding is examined. The effects of the fabrication processes on the material properties and their influence on the design of YF-12 wing panels are discussed.

Royster, D. M.; Wiant, H. R.; Bales, T. T.

1975-01-01

323

Synthesis of aluminium nitride\\/boron nitride composite materials  

Microsoft Academic Search

Aluminum nitride\\/boron nitride composite was synthesized by using boric acid, urea, and aluminum chloride (or aluminum lactate) as the starting compounds. The starting materials were dissolved in water and mixed homogeneously. Ammonolysis of this aqueous solution resulted in the formation of a precomposite gel, which converted into the aluminum nitride\\/boron nitride composite on further heat treatment. Characterization of both the

Tongsan D. Xiao; Kenneth E. Gonsalves; Peter R. Strutt

1993-01-01

324

Structure and Physical Properties of Natural Gellous Materials  

NASA Astrophysics Data System (ADS)

This study presents two types of natural gellous materials as cellulose resources including gellous material synthesized by Acetobacter xylinum in fermentation process of coconut water with common name Bacterial Cellulose (BC) and gellous material isolated from seed of Ocimum americanum called hydrogel. Morphological surface of BC and hydrogel was observed by Scanning Electron Microscope (SEM). These images show randomly arrangement of fibres in three dimensional network having length of 1-5 m and 3-12m, respectively in forming a dense reticulated structure. Hydrated fibres were observed evidently by Atomic Force Microscope (AFM) showing that BC and hydrogel have fibres in nanometer scale diameter, 7-10 and 2-3 nm, respectively. At glance, X-Ray diffraction profile of hydrogel shows broadening peaks at 2?, 16 and 22. While BC has peaks at 2?, 14.7, 16.7, 20.5 and 22.5, attributed to lattice diffractions (100), (010), and (110), respectively. The sharp profile present in BC lead to ordered structure, confirmed by higher crystallinity degree of BC (75%) compared to that`s of hydrogel (35%). Water Holding Capacity (WHC) of BC and hydrogel has values about 5.5 and 39.2 mL g-1, respectively while swelling ability of BC and hydrogel in water is 6.2 and 102.2%, respectively. Neutral sugar compositions of BC resulted in less 0.1% arabinose and rhamnose, 1.1% galactose, 98.5% glucose, 0.2 xylose and 0.2 mannose indicating high cellulose content. Meanwhile, hydrogel contains 11.9% (arabinose), 4.5% (rhamnose), 18.6% (galactose), 50.5% (glucose), 13.2% (xylose), 1.3% (mannose) indicating high hemicellulose contents leading to branching of arabinogalactan attached to cellulose.

Yudianti, Rike; Indrarti, Lucia; Azuma, Jun-Ichi

325

Ceramic matrix composites -- Advanced high-temperature structural materials  

SciTech Connect

This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base.

Lowden, R.A.; Ferber, M.K. [eds.] [Oak Ridge National Lab., Oak Ridge, TN (United States); Hellmann, J.R. [ed.] [Pennsylvania State Univ., University Park, PA (United States). Center for Advanced Materials; Chawla, K.K. [ed.] [New Mexico Inst. of Mining and Technology, Socorro, NM (United States); DiPietro, S.G. [ed.] [Textron Specialty Materials, Lowell, MA (United States)

1995-10-01

326

Glass-Containing Composite Materials. Alternative Reinforcement Concepts  

Microsoft Academic Search

Glass-containing composites with interpenetrating, graded or layered microstructures as well as hybrid glass and glass-ceramic\\u000a matrix composites are discussed. Aspects of their fabrication, microstructural characterisation, properties and applications\\u000a are reviewed. These materials have advantages regarding ease of processing and\\/or special properties which can be achieved,\\u000a in comparison with conventional dispersion-reinforced and fibre-reinforced glasses and glass-ceramics. The use of these materials

Aldo R. Boccaccini

327

Resistance fail strain gage technology as applied to composite materials  

NASA Technical Reports Server (NTRS)

Existing strain gage technologies as applied to orthotropic composite materials are reviewed. The bonding procedures, transverse sensitivity effects, errors due to gage misalignment, and temperature compensation methods are addressed. Numerical examples are included where appropriate. It is shown that the orthotropic behavior of composites can result in experimental error which would not be expected based on practical experience with isotropic materials. In certain cases, the transverse sensitivity of strain gages and/or slight gage misalignment can result in strain measurement errors.

Tuttle, M. E.; Brinson, H. F.

1985-01-01

328

Ceramic matrix composites -- Advanced high-temperature structural materials  

Microsoft Academic Search

This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for

R. A. Lowden; M. K. Ferber; J. R. Hellmann; K. K. Chawla; S. G. DiPietro

1995-01-01

329

Damage detection in composite materials using Lamb wave methods  

Microsoft Academic Search

Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents part of an experimental and analytical survey of candidate methods for in situ damage detection of composite materials. Experimental results are presented for the application of Lamb wave techniques to quasi-isotropic graphite\\/epoxy test specimens containing representative damage modes, including delamination, transverse ply cracks and

Seth S. Kessler; S. Mark Spearing; Constantinos Soutis

2002-01-01

330

Functional hybrid materials derived from natural cellulose  

NASA Astrophysics Data System (ADS)

In this paper, we report a study on the optical and the electrical properties of pure cotton fibers (CF) from chemically surface- and morphology-modified samples coated with poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) polymer by using a dip-coating method. The properties of the treated and coated fibers were characterized by using scanning electron microscopy (SEM), luminescence and I- V characteristics. The performance of fibers with MEH-PPV polymer as a coating component was investigated, and an excellent white-light emission that consisted of blue-, green-, and red-light-emitting bands was demonstrated. The I- V characteristics of sandwich-type devices consisting of successive layers of ITO (Indium doped tin oxide coated glass)-PEDOT-PSS (Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate)-CF/MEH-PPV-Ag showed that upon light illumination, the current increased in both the forward and the reverse bias conditions which suggest that the photoresponse parameters for the heterojunction are better than they are for the composite alone.

Zakirov, A. S.; Yuldashev, Sh. U.; Cho, H. D.; Lee, J. C.; Kang, T. W.; Khamdamov, J. J.; Mamadalimov, A. T.

2012-05-01

331

Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder  

NASA Astrophysics Data System (ADS)

Model graphite composites, similar to those used in nuclear applications as encasement material in fuel pebbles, were prepared by uniaxial cold compression moulding. They contained natural flake graphite, synthetic graphite and 20 wt.% phenolic novolac resin binder. The materials were carbonised at 900 C in a nitrogen atmosphere and then annealed at 1800 C in helium atmosphere. The X-ray diffraction studies showed that the graphite in these composites had hexagonal crystal structure after annealing. Raman spectroscopy revealed the presence of the structurally disordered phase derived from the carbonised resin. Optical microscopy revealed a flake-like microstructure for composites containing mainly natural graphite and needle-coke like particles for composites containing mainly synthetic graphite. The composites featured anisotropic property behaviour as the particles were partially aligned in a direction perpendicular to the compression direction. Thermogravimetric analysis studies showed that the annealed graphite composites were stable in air to 650 C. The linear thermal expansion coefficients measured by thermomechanical analysis (20-600 C) in the direction of pressing were in the range 5-9 10-6 K-1 and in the range 1.2-2 10-6 K-1 in the direction normal to pressing. The thermal conductivity of the composites were measured using Xenon flash method from 100 to 1000 C and the values ranged from 19 to 30 W m-1 K-1.

Magampa, P. P.; Manyala, N.; Focke, W. W.

2013-05-01

332

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite  

Microsoft Academic Search

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga, Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 411?m), provided the

F. Kusmanto; G. Walker; Q. Gan; P. Walsh; F. Buchanan; G. Dickson; M. McCaigue; C. Maggs; M. Dring

2008-01-01

333

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI), Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, roberto J.

2003-01-01

334

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI) Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, Roberto J.

2001-01-01

335

Light weight polymer matrix composite material  

NASA Technical Reports Server (NTRS)

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750 F in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Bowles, Kenneth J. (inventor); Lowell, Carl E. (inventor)

1988-01-01

336

Light weight polymer matrix composite material  

NASA Technical Reports Server (NTRS)

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

1991-01-01

337

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4-2.6 g/cm.sup.3 with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness, good abrasion resistance and crush strength.

Pearson, Alan (Murrysville, PA); Swansiger, Thomas G. (Apollo, PA)

1998-04-28

338

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process are disclosed for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4--2.6 g/cm{sup 3} with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness.

Pearson, A.; Swansiger, T.G.

1998-04-28

339

Application of thermosonics NDT in the detection of composite materials  

NASA Astrophysics Data System (ADS)

Composite materials have been applied widely in a lot of fields because of their excellent performance. And the composite materials may have some defects and be damaged in the process of manufacturing and usage, which will result in the performance degradation of the composite structure and even a failure. Thus, it is necessary to detect the defects of the composite materials. This paper introduced the thermosonics nondestructive testing technology, described the fundamental principle of the technology, and gave some experimental results of two kinds of composite materials. One of the two materials is carbon fiber foam sandwich composite material which has six pre-embedded debonding defects, and the other one is carbon fiber laminated board with the impact damage caused by collisions with different energies. And the testing results of the two materials by thermosonics are satisfactory. However, at present, the usual thermal wave imaging nondestructive testing technique for detecting composite materials is based on flash pulse excitation. In this paper, the carbon fiber laminated board was also detected by the pulsed method. And this paper further compared these two kinds of thermal wave imaging nondestructive testing techniques and the corresponding results with different excitation ways. Some differences could be found between these two methods by analyzing the results obtained by different excitation ways. Furthermore, based on the differences and the other factors such as the principles and devices of these two methods, we could summarize and know that these two methods have their respective advantages and disadvantages and could be applied to different situations. In the actual testing process, which method will be selected to detect the defects depends on the specific demands of the experiment and the characteristics of these two methods. And these two methods can also be used together to detect defects for a comprehensive and effective result.

Li, Yue; Zeng, Zhi; Chen, Dapeng; Xing, Chungfei; Tao, Ning; Zhang, Cunlin

2010-05-01

340

Interdisciplinary research concerning the nature and properties of ceramic materials  

NASA Technical Reports Server (NTRS)

The nature and properties of ceramic materials as they relate to solid state physics and metallurgy are studied. Special attention was given to the applications of ceramics to NASA programs and national needs.

1975-01-01

341

Multilayer Electroactive Polymer Composite Material Comprising Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

342

Acoustic emission from composite materials. [nondestructive tests  

NASA Technical Reports Server (NTRS)

The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique particularly well suited for the study of propagating cracks. Experiments are described in which acoustic emissions were unambiguously correlated with microstructural fracture mechanisms. The advantages and limitations of the AE technique are noted.

Visconti, I. C.; Teti, R.

1979-01-01

343

Accelerated hygrothermal stabilization of composite materials  

SciTech Connect

Experimentation validated a simple moisture conditioning scheme to prepare Gr/Ep composite parts for precision applications by measuring dimensional changes over 90 days. It was shown that an elevated temperature moisture conditioning scheme produced a dimensionally stable part from which precision structures could be built/machined without significant moisture induced dimensional changes after fabrication. Conversely, that unconditioned Gr/Ep composite panels exhibited unacceptably large dimensional changes (i.e., greater than 125 ppM). It was also shown that time required to produce stable parts was shorter, by more than an order of magnitude, employing the conditioning scheme than using no conditioning scheme (46 days versus 1000+ days). Two final use environments were chosen for the experiments: 50% RH/21C and 0% RH/21C. Fiberite 3034K was chosen for its widespread use in aerospace applications. Two typical lay-ups were chosen, one with low sensitivity to hygrothermal distortions and the other high sensitivity: [0, {plus_minus} 45, 90]s, [0, {plus_minus} 15, 0]s. By employing an elevated temperature, constant humidity conditioning scheme, test panels achieved an equilibrium moisture content in less time, by more than an order of magnitude, than panels exposed to the same humidity environment and ambient temperature. Dimensional changes, over 90 days, were up to 4 times lower in the conditioned panels compared to unconditioned panels. Analysis of weight change versus time of test coupons concluded that the out-of-autoclave moisture content of Fiberite 3034K varied between 0.06 and 0.1%.

Gale, J.A.

1994-05-01

344

Carbon-carbon composites: Emerging materials for hypersonic flight  

NASA Technical Reports Server (NTRS)

An emerging class of high temperature materials called carbon-carbon composites are being developed to help make advanced aerospace flight become a reality. Because of the high temperature strength and low density of carbon-carbon composites, aerospace engineers would like to use these materials in even more advanced applications. One application of considerable interest is as the structure of the aerospace vehicle itself rather than simply as a protective heat shield as on Space Shuttle. But suitable forms of these materials have yet to be developed. If this development can be successfully accomplished, advanced aerospace vehicles such as the National Aero-Space Plane (NASP) and other hypersonic vehicles will be closer to becoming a reality. A brief definition is given of C-C composites. Fabrication problems and oxidation protection concepts are examined. Applications of C-C composites in the Space Shuttle and in advanced hypersonic vehicles as well as other applications are briefly discussed.

Maahs, Howard G.

1989-01-01

345

Synopsis of Direct and Indirect Lightning Effects on Composite Materials  

NASA Technical Reports Server (NTRS)

NASA's Space Environments and Effects (SEE) Program funded a study on electromagnetic environmental effect issues of composite materials used by the aerospace industry. The results of which are published by Ross Evans, Tec-Masters Inc., in NASA-CR-4783, "Test Report - Direct and Indirect Lightning Effects on Composite Materials." Indirect effects include the electric and magnetic field shielding provided by a composite material illuminated by a near or direct lightning strike. Direct effects includes the physical damage of composites and/or assembly joint with a direct strike injection. This paper provides a synopsis of NASA-CR-4783. A short description is provided of the direct and indirect tests performed during the sturdy. General results and design guidelines are discussed.

Clark, Tony

1998-01-01

346

Structurally integrated fiber optic damage assessment system for composite materials.  

PubMed

Progress toward the development of a fiber optic damage assessment system for composite materials is reported. This system, based on the fracture of embedded optical fibers, has been characterized with respect to the orientation and location of the optical fibers in the composite. Together with a special treatment, these parameters have been tailored to yield a system capable of detecting the threshold of damage for various impacted Kevlar/epoxy panels. The technique has been extended to measure the growth of a damage region which could arise from either impact, manufacturing flaws, or static overloading. The mechanism of optical fiber fracture has also been investigated. In addition, the influence of embedded optical fibers on the tensile and compressive strength of the composite material has been studied. Image enhanced backlighting has been shown to be a powerful and convenient method of assessing internal damage to translucent composite materials. PMID:20555570

Measures, R M; Glossop, N D; Lymer, J; Leblanc, M; West, J; Dubois, S; Tsaw, W; Tennyson, R C

1989-07-01

347

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

348

COMPOSITE MATERIALS FATIGUE ISSUES IN WIND TURBINE BLADE CONSTRUCTION  

Microsoft Academic Search

This paper provides an overview of the results of recent studies of composite laminates of interest for wind turbine blade construction. In addition to the primary requirements of stiffness, strength, and ease of processing, wind blade materials must withstand severe fatigue loading under service environments. The large material volumes and cost constraints also lead to unusually thick plies and fabrics,

John F. Mandell; Daniel D. Samborsky

349

Insertion loss of sound waves through composite acoustic window materials  

Microsoft Academic Search

This study evaluated the insertion loss of sound waves through composite acoustic window materials for sonar dome applications, and examined the influence of dome shape on the sonar performance. The insertion loss of sound waves through acoustic window materials was experimentally measured as a function of frequency at normal incidence. The insertion loss was also theoretically estimated with three- and

Ji-Hye Lee; Byoung-Nam Kim; Ku-Kyun Shin; Suk Wang Yoon

2010-01-01

350

Novel Composite Shielding Materials for Supression of Microwave Radiation  

Microsoft Academic Search

In this paper we describe a novel approach for shielding composite materials synthesis that is based on formation of micro-and nano-sized volumes of microwave absorbing media in fiber matrix. Such method allows fixation of liquid and solid phases in flexible basis and creation of materials with \\

V. Bogush; T. Borbot'ko; N. Kolbun; L. Lynkov

2006-01-01

351

Characterization of ceramic composite materials for gas turbine applications  

Microsoft Academic Search

Ceramic composite materials have the capability to sustain high stress in the presence of high temperatures and aggressive atmospheres. Such materials are being considered for application as cumbustors, burner cubes, heat exchangers, headers. hot-gas filters, and even rotors of stationary gas turbine engines. In the present program, Nicalon preforms of tubular geometry were fabricated with different fiber architectures (filament winding,

K. Reifsnider; W. Stinchcomb; K. Liao; L. Oleksuk; D. Stinton

1993-01-01

352

Measurement of Damping of Composite Materials for Turbomachinery Applications.  

National Technical Information Service (NTIS)

The scientific community has felt that ceramic matrix composite (CMC) materials possess more material damping than the superalloys used in the production of rocket engine turbomachinery turbine-end components. The purpose of this NASA/MFSC study is to qua...

D. L. Harris

1998-01-01

353

On Low-Velocity Impact Testing of Composite Materials  

Microsoft Academic Search

The importance of understanding the response of structural composites to impact cannot be overstated. This understanding includes both the impact phenomena themselves and the influence of materials properties on the impact response. This paper presents the need for instrumented testing to optimize our understanding of the impact event, especially the response of the impacted material. The conclusion is drawn that

Peter O. Sjoblom; J. Timothy Hartness; Tobey M. Cordell

1988-01-01

354

Natural Radioactivity of Quarry raw Material in Israel  

NASA Astrophysics Data System (ADS)

During the past decade Natural Occurring Radioactive Material (NORM) has been receiving growing attention by radiation protection agencies, including chronic exposure to radon and radiation from building materials. A new Israeli standard (5098) which limit the radionuclide concentration in building material entered into force in 2003. Building materials are often made of natural raw materials which contain natural radionuclides from the 238U-226Ra, 232Th decay series and 40K that occur naturally in the Earth's crust. The radionuclide concentration in the building material depends on the source of the raw material, manufacturing process and the addition of technically enhanced NORM (Te NORM) like fly ash, phospho-gypsum, etc. The aim of this study was to investigate the spatial variation of the natural radioactivity in quarries in Israel, the dependency on the type of quarried substance and to asses the raw materials by radiation protection criteria. The study covered a total of 25 quarries all over Israel that manufacture different types of quarried substances (Limestone, Dolomite, Basalt, Gypsum etc.). Each of the quarries was sampled for three different aggregate sizes. The quarries were selected according to geological-geographical criteria such that all types of quarried materials throughout Israel will be investigated. The radionuclide measurement was performed by Gamma spectrometry according to standard procedures. A simulation was carried out on different concrete mixtures to asses the individual effective dose from the building materials. Results indicate large variations in the radionuclide concentration of raw materials in Israel. An optimization based on radiation protection criteria is proposed to minimize radiation exposure from building material.

Haquin, G.; Gazit-Yaari, N.; Yungreis, Z.; Braun, M.; Margaliot, M.

2004-12-01

355

Collagen/hydroxyapatite composite materials with desired ceramic properties.  

PubMed

Our purpose was to obtain and characterize some collagen/hydroxyapatite (COLL/HA) hybrid composite materials with desired ceramic properties. The ceramic properties of these materials were achieved by combining two drying methods: controlled air drying at 30C followed by freeze-drying. Through the function of the air drying times, the materials morphology varies from porous materials (when the materials are freeze-dried) up to dense materials (when the materials are air-dried), while the combined drying allows us to obtain an intermediary morphology. The composite materials intended to be used as bone grafts and in a drug delivery system were characterized by XRD, FTIR, SEM, and also by determining the ceramic properties by using the Arthur method. The ceramic properties of these COLL/HA composite materials vary in large range, for instance the density of the materials varies from 0.06 up to 1.5g/cm(3) while the porosity varies from 96.5% down to 27.5%. PMID:21415027

Andronescu, Ecaterina; Voicu, Georgeta; Ficai, Maria; Mohora, Ioana Anita; Trusca, Roxana; Ficai, Anton

2011-01-01

356

Workshop on Scaling Effects in Composite Materials and Structures  

NASA Technical Reports Server (NTRS)

This document contains presentations and abstracts from the Workshop on Scaling Effects in Composite Materials and Structures jointly sponsored by NASA Langley Research Center, Virginia Tech, and the Institute for Mechanics and Materials at the University of California, San Diego, and held at NASA Langley on November 15-16, 1993. Workshop attendees represented NASA, other government research labs, the aircraft/rotorcraft industry, and academia. The workshop objectives were to assess the state-of-technology in scaling effects in composite materials and to provide guidelines for future research.

Jackson, Karen E. (compiler)

1994-01-01

357

Materials Science and Technology Teacher's Handbook: Experiments/Demonstrations: Composites  

NSDL National Science Digital Library

This chapter from the Materials Science and Technology Teacher's Handbook provides experiments and demonstrations involving composites that can be used in a materials science and technology curriculum. These experiments are "designed to grab studentsâ attention, pull their minds from predictable everyday classroom activities, give them something to look forward to, and teach them some simple principles and properties used by materials scientists." Experiments include Making Concrete, Simple Stressed-Skin Composite, Airfoils, and Making Paper. Drawings and diagrams help illustrate the concepts. This document will serve as a framework for instructors and may be downloaded in PDF format.

2012-10-05

358

Emissivity Results on High Temperature Coatings for Refractory Composite Materials  

NASA Technical Reports Server (NTRS)

The directional emissivity of various refractory composite materials considered for application for reentry and hypersonic vehicles was investigated. The directional emissivity was measured at elevated temperatures of up to 3400 F using a directional spectral radiometric technique during arc-jet test runs. A laboratory-based relative total radiance method was also used to measure total normal emissivity of some of the refractory composite materials. The data from the two techniques are compared. The paper will also compare the historical database of Reinforced Carbon-Carbon emissivity measurements with emissivity values generated recently on the material using the two techniques described in the paper.

Ohlhorst, Craig W.; Vaughn, Wallace L.; Daryabeigi, Kamran; Lewis, Ronald K.; Rodriguez, Alvaro C.; Milhoan, James D.; Koenig, John R.

2007-01-01

359

Phase interaction in composite materials Zr-Mo, W  

SciTech Connect

The influence of elevated temperatures on zirconium matrix composites reinforced by molybdenum and tungsten fibers was studied to determine the temperature-time boundaries of the stability of the materials. Starting materials were sheets of zirconium iodide obtained by cold rolling. Specimens were produced by compacting sandwich type preforms using diffusion welding in vacuum. Component diffusion and distribution after annealing were studied using x-ray microanalysis. Diffusion coefficients were calculated. Microstructures are shown. The composites possessed satisfactory kinetic stability up to 1373/sup 0/K and at higher temperatures demonstrated intense interaction between fiber and matrix materials involving the formation of solid solutions and intermetallic phases.

Karpinos, D.M.; Vishnyakov, L.R.; Moroz, V.P.; Bondarenko, T.N.; Dzeganovskii, V.P.

1988-05-01

360

Characterization of cryogenic microcracking in carbon fiber/epoxy composite materials  

NASA Astrophysics Data System (ADS)

Polymeric composite materials have been widely utilized to take advantage of their large specific strength and stiffness. These characteristics have made them attractive for use in aerospace applications as containment structures for cryogenic fluids. However, the anisotropic, heterogeneous, and viscoelastic nature of polymeric composite materials creates a unique set of challenges for the storage of cryogenic fluids. Mismatches in thermal expansion between the fibers and the matrix in these materials result in the generation of thermal stresses at low temperatures that can ultimately cause failure in the form of microcracks that propagate throughout the material, degrading performance. This work examined the phenomenological and theoretical aspects of microcrack formation in carbon fiber/epoxy composite materials at low temperatures. Microcrack formation was initially investigated using an experimental approach. The role of the fiber and matrix type in microcracking was studied, along with the interaction between the fibers and the matrix and the effects of nanoparticle matrix modification. It was found that the fiber and matrix type had significant effects on microcrack formation, with decreased fiber moduli, decreased matrix coefficient of thermal expansion, nanoparticle modification, rubber toughening, and increased adhesion all corresponding to reduced microcracking. These improvements were achieved by reducing the thermal stresses in the materials studied and increasing the failure resistance of the laminates. It was found that the processing conditions of a laminate, namely the cure temperature, had a direct impact on microcracking by changing the stress free temperature of a material and the corresponding thermal stresses at cryogenic temperatures. The analysis of the variables that contributed to microcrack formation was used to develop a stress-based compound beam model to predict the onset temperature for microcracking in composite materials. This model was unique in that it accounted for the variation in material properties at low temperatures. Collectively, this work examined the phenomena behind the cryogenic microcracking of composite materials and applied this information to develop a predictive model for low temperature failure of composite materials from thermal stress generation.

Timmerman, John Francis

361

Biotransformation of an uncured composite material  

NASA Technical Reports Server (NTRS)

The feasibility of biologically degrading prepreg wastes was studied. The work was conducted with the intention of obtaining baseline data that would facilitate the achievement of two long-range goals. These goals are: (1) the biological remediation of the hazardous components in the prepreg wastes, and (2) providing the potential for recycling the prepreg waste fibers. The experiments examined a prepreg that employs an bismaleimide resin system. Initial results demonstrated an obvious deterioration of the prepreg material when incubated with several bacterial strains. The most active cultures were identified as a mixture of 'Bacillus cereus' and 'Pseudomonas sp'. Gas chromatography analyses revealed seven primary compounds in the resin mixture. Biotransformation studies, using the complete prepreg material, demonstrated on obvious loss of all seven organic compounds. Gas chromatography-mass spectrometry analyses resulted in structure assignments for the two primary components of the resin. Both were analogs of Bisphenol A; one being bismaleimide, and the other being Bisphenol A containing a diglycidyl moiety. The 'diglycidyl analog' was purified using thin-layer chromatography and the biotransformation of this compound (at 27 ug/ml bacterial culture) was monitored. After a seven-day incubation, approximately 40% of the organic compound was biotransformed. These results demonstrate the biotransformation of the prepreg resin and indicate that biological remediation of the prepreg wastes is feasible.

Welsh, Clement J.; Glass, Michael J.; Cheslack, Brian; Pryor, Robert; Tran, Duan K.; Bowers-Irons, Gail

1994-01-01

362

Thermal radiation transmission through composite material  

NASA Astrophysics Data System (ADS)

On 10 June 1993, the Defense Nuclear Agency (DNA) Field Command at White Sands Missile Range conducted a Thermal Radiation Simulator (TRS) test for the Naval Surface Warfare Center (NSWC) during project MINOR UNCLE. The NSWC was interested in measuring the radiant thermal energy absorbed by a fiberglass panel during a simulated nuclear weapon event. The resultant thermocouple data showed an unusual initial high-temperature rise and fall, followed by the expected conductive heating. The initial transient was theorized to be the result of thermal radiation transmitted through the panel. To investigate this theory, NSWC prepared several more panels of different thicknesses, preinstrumented with thermocouples and strain gages for testing with a U.S. Army Research Laboratory (ARL) TRS. ARL also provided additional instrumentation to measure thermal radiation on the front surface as well as behind the panel. The results showed that there was direct heating of the rear of the composite panel by thermal radiation. The quantity of heat transmission through the panel and the point of ignition of the front surface of the panel were determined. Smoke and charring of the front surface protected the panel from further heating and possible destruction.

Loucks, Richard B.

1995-06-01

363

A grammatical approach to customization of shape and composite materials  

NASA Astrophysics Data System (ADS)

With the increasing use of composite materials in Mechanical and Aerospace industries, an approach is required to facilitate designing of components using composite materials, while ensuring customization of the shape such a way that multiple design goals for the components are satisfied. Existing design methods may be used in some cases, where the component shape and loadings are simple. While a significant amount of research has been conducted to study the properties of composite materials, little attention has been paid to find out a design approach such that (1) the user requirements in the very general form may be used directly and as the input for the design, (2) the best possible composite material are selected to meet multiple desired functions, and (3) shape variation is analyzed in order to enable mass customization of the design. Thus an approach is required that will be able to handle both the shape and the material in order to design a load bearing component using composite materials. In this research the focus is to develop a design approach that will consider the user requirements for a composite component in its very general form and generate component shape and material details in a systematic order so that the designed component can withstand a given loading condition. Consequently, the Primary Research Question is: How to simultaneously explore shape and composite materials during the design of a product to meet multiple property and functional goals? The wide range of properties, covered by various fiber-matrix combinations, along with their directional property characteristics, maximizes the flexibility of the designers, while designing composite material products. Meeting multiple property goals, however, complicates the design process as both the composite material selection and the component shape formation becomes highly intricate with the loading conditions and a number of matrix calculations needs to be performed to determine theoretical value of composite material properties. A grammar is a formal definition of a language written in transformational form. To address these issues, in this research a grammatical approach is developed that will generate a shape grammar to perform shape optimization, and then incorporate a composite material selection system and loading analysis techniques of Solid Mechanics in order to design load bearing components of irregular shape. The approach will be able to consider the user requirements in the very general text form, convert them to the design requirements for the component, generate optimized shape based on multiple design constraints, perform the complete design work, and generate the component. The major contributions include: (1) generating a shape grammar to represent functions of the load bearing component such a way that mass-customization of shape is possible, (2) developing a composite material customization system in order to satisfy directional property requirements, and (3) introducing a unique laminate design approach in order to satisfy design property requirements at the critical cross-sections locally that can result in highly efficient design compared to conventional design method. Verification of the approach will focus on its application to simultaneously explore shapes and customization of composite materials.

Nandi, Soumitra

364

Measurement of Damping of Composite Materials for Turbomachinery Applications  

NASA Technical Reports Server (NTRS)

The scientific community has felt that ceramic matrix composite (CMC) materials possess more material damping than the superalloys used in the production of rocket engine turbomachinery turbine-end components. The purpose of this NASA/MFSC study is to quantify the damping in CMC's as compared to a typical super-alloy, Inconel 718. It was observed through testing of beam coupons and disk specimens that the CMC's do indeed possess more material damping than the baselined alloy Inconel 718.

Harris, D. L.

1998-01-01

365

Application of laser ultrasonics to graphite\\/polymer composite materials  

Microsoft Academic Search

The development and application of a laser-based ultrasonic inspection system for noncontact evaluation of graphite\\/polymer composite materials has been realized. The use of lasers to generate and detect ultrasonic waveforms in materials provides a means to detect material properties remotely. The study consisted of three main aspects: (1). A confocal Fabry-Perot (CFP) based ultrasonic detection system has been developed which

James Norbert Caron

1997-01-01

366

Tensile Strength of Natural Fiber Reinforced Polyester Composite  

NASA Astrophysics Data System (ADS)

Nowadays, increasing awareness of replacing synthetic fiber such as glass fiber has emerged due to environmental problems and pollutions. Automotive manufacturers also seek new material especially biodegradable material to be non-load bearing application parts. This present work discussed on the effect of silane treatment on coir fiber reinforced composites. From the results of tensile tests, fibers treated with silane have attained maximum material stiffness. However, to achieve maximum ultimate tensile strength and strain at failure performances, untreated fibers work very well through fiber bridging and internal friction between fiber and polymeric matrix. Scanning electron microscope (SEM) observations have coincided with these results.

Ismail, Al Emran; Awang, Muhd. Khairudin; Sa'At, Mohd Hisham

2007-05-01

367

The updated IAEA database of natural matrix reference materials  

Microsoft Academic Search

The International Atomic Energy Agency (IAEA) maintains a database of biological and environmental reference materials of natural origin (human and animal tissues, foods, plants, soils, sediments, etc.) for trace elements, radionuclides, stable isotopes, organic contaminants and other related measurands. The purpose is to help analysts to select reference materials for quality assurance purposes that match as closely as possible (i.e.,

A. R. Bleise; B. Smodi; D. Glavic-Cindro; R. M. Parr

2001-01-01

368

A new technique for simulating composite material  

NASA Technical Reports Server (NTRS)

This project dealt with the development on new methodologies and algorithms for the multi-spectrum electromagnetic characterization of large scale nonmetallic airborne vehicles and structures. A robust, low memory, and accurate methodology was developed which is particularly suited for modern machine architectures. This is a hybrid finite element method that combines two well known numerical solution approaches. That of the finite element method for modeling volumes and the boundary integral method which yields exact boundary conditions for terminating the finite element mesh. In addition, a variety of high frequency results were generated (such as diffraction coefficients for impedance surfaces and material layers) and a class of boundary conditions were developed which hold promise for more efficient simulations. During the course of this project, nearly 25 detailed research reports were generated along with an equal number of journal papers. The reports, papers, and journal articles are listed in the appendices along with their abstracts.

Volakis, John L.

1991-01-01

369

Fracture toughness of fibrous composite materials  

NASA Technical Reports Server (NTRS)

Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

Poe, C. C., Jr.

1984-01-01

370

The role of polymer based composites materials in modern and future aerospace structures  

NASA Astrophysics Data System (ADS)

The need to reduce the overall weight of aeronautical and space structures, while at the same time preserving or even improving their performances, make the research and development in the field of innovative structures and advanced composite materials a crucial step for the advancement of aerospace technologies. Several fields of innovation have been explored in the last decades but the most promising solutions for the future of aerospace structures will be found in the "intelligent" use of polymer based composite materials both in the design and in their "nature like" use.

Cantoni, Stefania; De Nicola, Felice; Mercurio, Umberto; Quaranta, Vincenzo

2014-05-01

371

Review on advanced composite materials boring mechanism and tools  

NASA Astrophysics Data System (ADS)

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Shi, Runping; Wang, Chengyong

2010-12-01

372

Probabilistic fatigue life prediction of metallic and composite materials  

NASA Astrophysics Data System (ADS)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

373

Composite materials research and education program: The NASA-Virginia Tech composites program  

NASA Technical Reports Server (NTRS)

Major areas of study include: (1) edge effects in finite width laminated composites subjected to mechanical, thermal and hygroscopic loading with temperature dependent material properties and the influence of edge effects on the initiation of failure; (2) shear and compression testing of composite materials at room and elevated temperatures; (3) optical techniques for precise measurement of coefficients of thermal expansion of composites; (4) models for the nonlinear behavior of composites including material nonlinearity and damage accumulation and verification of the models under biaxial loading; (5) compressive failure of graphite/epoxy plates with circular holes and the buckling of composite cylinders under combined compression and torsion; (6) nonlinear mechanical properties of borsic/aluminum, graphite/polyimide and boron/aluminum; (7) the strength characteristics of spliced sandwich panels; and (8) curved graphite/epoxy panels subjected to internal pressure.

Herakovich, C. T.

1980-01-01

374

Modular design in natural and biomimetic soft materials.  

PubMed

Under eons of evolutionary and environmental pressure, biological systems have developed strong and lightweight peptide-based polymeric materials by using the 20 naturally occurring amino acids as principal monomeric units. These materials outperform their man-made counterparts in the following ways: 1) multifunctionality/tunability, 2) adaptability/stimuli-responsiveness, 3) synthesis and processing under ambient and aqueous conditions, and 4) recyclability and biodegradability. The universal design strategy that affords these advanced properties involves "bottom-up" synthesis and modular, hierarchical organization both within and across multiple length-scales. The field of "biomimicry"-elucidating and co-opting nature's basic material design principles and molecular building blocks-is rapidly evolving. This Review describes what has been discovered about the structure and molecular mechanisms of natural polymeric materials, as well as the progress towards synthetic "mimics" of these remarkable systems. PMID:21898722

Kushner, Aaron M; Guan, Zhibin

2011-09-19

375

Optimization of internal damping in fiber reinforced composite materials  

SciTech Connect

This dissertation describes new, reliable, and fast impulse techniques for characterization of damping in fiber reinforced composite materials. Flexural and extensional vibration tests are used for determination of complex moduli of aligned discontinuous fiber composite, and off axis fiber composite specimens, respectively. The results from these tests are then compared with theoretical predictions from micromechanics models based on a single fiber. The analytical model is fitted to the experimental results by varying certain parameters that have uncertainties associated with them. It is shown that improved damping can be obtained with very low fiber aspect ratios, and that even better damping properties are possible with off-axis fibers. These results were obtained from tests done on three different fiber reinforced composite materials: graphite/epoxy, Kevlar/epoxy and boron/epoxy.

Suarez, S.A.

1985-01-01

376

Improved Composites Using Crosslinked, Surface-Modified Carbon Nanotube Materials  

NASA Technical Reports Server (NTRS)

Individual carbon nanotubes (CNTs) exhibit exceptional tensile strength and stiffness; however, these properties have not translated well to the macroscopic scale. Premature failure of bulk CNT materials under tensile loading occurs due to the relatively weak frictional forces between adjacent CNTs, leading to poor load transfer through the material. When used in polymer matrix composites (PMCs), the weak nanotube-matrix interaction leads to the CNTs providing less than optimal reinforcement.Our group is examining the use of covalent crosslinking and surface modification as a means to improve the tensile properties of PMCs containing carbon nanotubes. Sheet material comprised of unaligned multi-walled carbon nanotubes (MWCNT) was used as a drop-in replacement for carbon fiber in the composites. A variety of post-processing methods have been examined for covalently crosslinking the CNTs to overcome the weak inter-nanotube shear interactions, resulting in improved tensile strength and modulus for the bulk sheet material. Residual functional groups from the crosslinking chemistry may have the added benefit of improving the nanotube-matrix interaction. Composites prepared using these crosslinked, surface-modified nanotube sheet materials exhibit superior tensile properties to composites using the as received CNT sheet material.

Baker, James Stewart

2014-01-01

377

Simulation of composite material response under dynamic compressive loading  

SciTech Connect

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the study is confined to glass fiber/epoxy composites. The technique uses a numerical model of a representative sample of the microstructure with randomly distributed fibers. By subjecting the boundary of this numerical sample to prescribed loading histories, a statistical interpretation allows prediction of the global material response. Because the events at the microstructural scale involve locally large deformation, and because of the constantly changing picture with regard to contact between the fibers, the Eulerian code CTH is used for these calculations. Certain aspects of material failure can also be investigated using this approach. The method allows the mechanical behavior of composite materials to be studied with fewer assumptions about constituent behavior and morphology than typically required in analytical efforts.

Silling, S.A.; Taylor, P.A.

1993-12-31

378

Les Composites: Utilisateur et Producteur (Composite Materials: The User and the Producer).  

National Technical Information Service (NTIS)

International competition requires the aircraft manufacturer to be constantly on the look out for recent construction materials having the best performance, mass, and cost. Carbon-resin composites are a good comprise for aircraft structures. Currently int...

R. Radondy Tremillo

1984-01-01

379

Particle size effect on the complex permeability for permalloy composite materials  

SciTech Connect

Complex permeability {mu}* = {mu}{prime}-i{mu}{double{underscore}prime} of permalloy (Fe{sub 0.55}Ni{sub 0.45}) composite materials has been studied in the frequency range from 10kHz to 2GHz for two different particle sizes of permalloys (particle diameter d < 45{micro}m and d < 6{micro}m). Low frequency permeabilities of small particle composites have larger values than those of large particle ones and natural resonance frequency of small particle composites is lower than that of large particle ones. The ac electrical resistivity in low frequency range shows a drastic increase at about 40 vol% permalloy content with decreasing permalloy content indicating the disconnection of embedded permalloy particles. These properties can be realized considering the eddy current in composite materials.

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

1999-09-01

380

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

Microsoft Academic Search

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing

Hansang Kwon; Seungchan Cho; Marc Leparoux; Akira Kawasaki

2012-01-01

381

High-specific-energy composite-material flywheel. Final report  

SciTech Connect

A flywheel rotor has been designed and fabricated to demonstrate energy densities ranging from 50.6 watt-hour/kg (23 watt-hour/lb) to 88 watt-hour/kg (40 watt-hour/lb). The design is composed of a multiring rim made of S-2 glass/epoxy and Kevlar/epoxy composite materials, mounted on a four-spoke aluminum and graphite/epoxy composite hub. Ten flywheel rotors were produced for test.

Not Available

1983-03-29

382

Experimental Investigation of Textile Composite Materials Using Moire Interferometry  

NASA Technical Reports Server (NTRS)

The viability as an efficient aircraft material of advanced textile composites is currently being addressed in the NASA Advanced Composites Technology (ACT) Program. One of the expected milestones of the program is to develop standard test methods for these complex material systems. Current test methods for laminated composites may not be optimum for textile composites, since the architecture of the textile induces nonuniform deformation characteristics on the scale of the smallest repeating unit of the architecture. The smallest repeating unit, also called the unit cell, is often larger than the strain gages used for testing of tape composites. As a result, extending laminated composite test practices to textiles can often lead to pronounced scatter in material property measurements. It has been speculated that the fiber architectures produce significant surface strain nonuniformities, however, the magnitudes were not well understood. Moire interferometry, characterized by full-field information, high displacement sensitivity, and high spatial resolution, is well suited to document the surface strain on textile composites. Studies at the NASA Langley Research Center on a variety of textile architectures including 2-D braids and 3-D weaves, has evidenced the merits of using moire interferometry to guide in test method development for textile composites. Moire was used to support tensile testing by validating instrumentation practices and documenting damage mechanisms. It was used to validate shear test methods by mapping the full-field deformation of shear specimens. Moire was used to validate open hole tension experiments to determine the strain concentration and compare then to numeric predictions. It was used for through-the-thickness tensile strength test method development, to verify capabilities for testing of both 2-D and 3-D material systems. For all of these examples, moire interferometry provided vision so that test methods could be developed with less speculation and more documentation.

Ifju, Peter G.

1995-01-01

383

Grained composite materials prepared by combustion synthesis under mechanical pressure  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

384

Effects of thermal cycling on composite materials for space structures  

NASA Technical Reports Server (NTRS)

The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.

Tompkins, Stephen S.

1989-01-01

385

Radiopacity of experimental composite resins containing radiopaque materials.  

PubMed

This study aimed to investigate the relationship between the radiopacity of an experimental light-cured composite resin and the amount and type of its radiopaque material: Ti, SrCO3, ZrO2, BaSO4, or Bi2O3. Radiopacity of each material was evaluated in terms of aluminum equivalent thickness using an aluminum step wedge. Then, the half-value layer thickness of the experimental composite resin, which had an aluminium equivalent thickness of 1 mm, was evaluated. It was found that the effects of elemental composition were not identical when evaluated in terms of aluminum equivalent thickness and by half-value layer. Nevertheless, both measurement methods indicated that radiopacity increased with increase in radiopaque material content as well as increase in atomic number of the element. PMID:16279720

Aoyagi, Yujin; Takahashi, Hidekazu; Iwasaki, Naohiko; Honda, Ei-ichi; Kurabayashi, Toru

2005-09-01

386

Pin bearing evaluation of LTM25 composite materials  

NASA Technical Reports Server (NTRS)

This report summarizes pin bearing evaluations of LTM25 composite materials. Northrop Grumman Corporation conducted pin bearing testing and fabricate two panels from composite materials that cure at low temperatures. These materials are being incorporated into Unmanned Aerial Vehicles (UAVS) to reduce manufacturing costs since they allow the use of low-cost tooling and facilities. Two composite prepreg product forms were evaluated; MR50/LTM25 unidirectional tape, batch 2881vd and CFS003/LTM25 woven cloth, batch 2216. Northrop Grumman fabricated, machined, and tested specimens to determine the bearing strength in accordance with MIL-HDBK-17D, Volume 1, Section 7.2.4. Quasi-isotropic laminates from the two product forms were fabricated for these tests. In addition, 2 quasi-isotropic panels of dimensions 12 in. x 28 in. were fabricated (one each from the two product forms), inspected, and shipped to NASA Langley for further evaluation.

Shah, C. H.; Postyn, A. S.

1996-01-01

387

Brazing of sheet composite materials with aluminium matrix  

NASA Astrophysics Data System (ADS)

The technique of brazing composite sheets with an aluminum matrix is investigated for Al matrices with either stainless steel or boron fibers. Brazing is compared to other joining techniques, and the relationship between heating and pressure levels is studied by characterizing the joint qualities microscopically. Solder composition is similarly analyzed, and brazing recommendations are given for ranges of joint sizes. Calculations of the temperature fields for the brazing of these composite materials yield specific-heat input data. Optimal brazing modes thus derived for the Al-matrix composites yield joints free of the intermetallide phases that degrade the performance of brazed structures. The tensile strength of the optimized joints is shown to be good relative to the strength of the original composites with Al matrices.

Khorunov, V. F.; Kuchuk-Iatsenko, V. S.; Dykhno, I. S.; Kasatkina, N. V.

388

Natural radioactivity measurements of building materials in Baotou, China.  

PubMed

Natural radioactivity due to (226)Ra, (232)Th and (40)K in the common building materials collected from Baotou city of Inner Mongolia, China was measured using gamma-ray spectrometry. The radiation hazard of the studied building materials was estimated by the radium equivalent activity (Ra(eq)), internal hazard index (H(in)) and annual effective dose (AED). The concentrations of the natural radionuclides and Ra(eq) in the studied samples were compared with the corresponding results of other countries. The Ra(eq) values of the building materials are below the internationally accepted values (370 Bq kg(-1)). The values of H(in) in all studied building materials are less than unity. The AEDs of all measured building materials are at an acceptable level. PMID:22522177

Zhao, Caifeng; Lu, Xinwei; Li, Nan; Yang, Guang

2012-12-01

389

Hot extruded carbon nanotube reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics.

Kwon, Hansang; Leparoux, Marc

2012-10-01

390

Anode materials for sour natural gas solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

Novel anode catalysts have been developed for sour natural gas solid oxide fuel cell (SOFC) applications. Sour natural gas comprises light hydrocarbons, and typically also contains H2S. An alternative fuel SOFC that operates directly on sour natural gas would reduce the overall cost of plant construction and operation for fuel cell power generation. The anode for such a fuel cell must have good catalytic and electrocatalytic activity for hydrocarbon conversion, sulfur-tolerance, resistance to coking, and good electronic and ionic conductivity. The catalytic activity and stability of ABO3 (A= La, Ce and/or Sr, B=Cr and one or more of Ti, V, Cr, Fe, Mn, or Co) perovskites as SOFC anode materials depends on both A and B, and are modified by substituents. The materials have been prepared by both solid state and wet-chemical methods. The physical and chemical characteristics of the materials have been fully characterized using electron microscopy, XRD, calorimetry, dilatometry, particle size and area, using XPS and TGA-DSC-MS. Electrochemical performance was determined using potentiodynamic and potentiostatic cell testing, electrochemical impedance analysis, and conductivity measurements. Neither Ce0.9Sr0.1VO3 nor Ce0.9 Sr0.1Cr0.5V0.5O3 was an active anode for oxidation of H2 and CH4 fuels. However, active catalysts comprising Ce0:9Sr0:1V(O,S)3 and Ce0.9Sr 0.1Cr0.5V0.5(O,S)3 were formed when small concentrations of H2S were present in the fuels. The oxysulfides formed in-situ were very active for conversion of H2S. The maximum performance improved from 50 mW cm-2 to 85 mW cm -2 in 0.5% H2S/CH4 at 850C with partial substitution of V by Cr in Ce0.9Sr0.1V(O,S)3. Selective conversion of H2S offers potential for sweetening of sour gas without affecting the hydrocarbons. Perovskites La0.75Sr0.25Cr0.5X 0.5O3--delta, (henceforth referred to as LSCX, X=Ti, Mn, Fe, Co) are active for conversion of H2, CH4 and 0.5% H2S/CH4. The order of activity in the different fuels depends on the substituent element: CH4, X = Fe>Mn>Ti; H 2, X = Fe>Mn>Ti; and 0.5% H2S/CH4, X = Fe>Ti>Mn. The electrocatalytic activity for methane oxidation in a fuel cell correlates with ex-situ temperature programmed catalytic activity. A process is proposed to explain the difference in catalyst order and enhanced activities in H 2S/CH4 as fuel compared to CH4 alone. The maximum power density of 250 mW cm-2 was attained using a fuel cell with a composite anode, LSCFe-GDC | YSZ(0.3 mm) | Pt, operated at 850C (GDC is Ce0.9Gd0.1O3, a good mixed conductor under reducing conditions).

Danilovic, Nemanja

391

Effective thermal conductivity of a thin, randomly oriented composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thicknesses. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relative low thermal conductivity. The results indicate that, below some threshold thickness, the composite thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between the filler and matrix thermal conductivities.

Phelan, P.E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States). Energy Technology Div.

1997-10-01

392

Effective thermal conductivity of a thin composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thickness. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. Results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between filler and matrix thermal conductivities.

Phelan, P.E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States)

1996-12-31

393

Composite Overwrapped Pressure Vessels (COPV) Materials Aging Issues  

NASA Technical Reports Server (NTRS)

This slide presentation reviews some of the issues concerning the aging of the materials in a Composite Overwrapped Pressure Vessels (COPV). The basic composition of the COPV is a Boss, a composite overwrap, and a metallic liner. The lifetime of a COPV is affected by the age of the overwrap, the cyclic fatigue of the metallic liner, and stress rupture life, a sudden and catastrophic failure of the overwrap while holding at a stress level below the ultimate strength for an extended time. There is information about the coupon tests that were performed, and a test on a flight COPV.

2010-01-01

394

Deformation of adaptive materials. Part II. Adaptive composite  

NASA Astrophysics Data System (ADS)

A new class of materials, layer composites containing adaptive polydomain components, is considered. Polydomain structures can be the result of constrained phase transformation. Polydomain structures consist of periodically alternating layers of different stable and metastable phases (heterophase polydomain) or differently oriented domains of product phase (e.g. polytwin). The domain interface movement enables an additional mode of deformation. The theory predicts unusual physical and mechanical properties of composites, particularly, considerable decrease of the effective elastic moduli of composites, nonlinear stress-strain relations, and critical behavior at small thickness of an active layer.

Roytburd, Alexander L.; Slutsker, Julia

1999-09-01

395

An isoelastic prosthesis using a new composite material.  

PubMed

A new particulate composite material has been assessed with regard to the design of an 'isoelastic' or 'modulus matched' hip prosthesis. Three different prototype designs were assessed, each of which consisted of a femoral component made from the composite material, attached to a metal ball via a metal 'spike' insert. The prototypes varied in terms of the detailed shape of the spike, which was modified in the light of photoelastic stress analysis, so as to produce a more acceptable stress distribution to the composite material in the proximal region. Prototypes were made by hand moulding and by transfer moulding; both methods produced defects of various kinds. Simulation tests were conducted using a model of the proximal femur constructed from glass fibre composite, cyclically loaded in a servo-hydraulic testing machine. Though some difficulties were experienced with defective mouldings, especially for the transfer moulding process, a clear improvement was demonstrated for the final (Mark III) design. The fatigue endurance of this prototype was similar to that of conventional metal prostheses tested under similar conditions. Fatigue crack propagation tests were carried out on samples of the composite material to establish its propagation threshold. These results were combined with a finite element stress analysis and fracture mechanics theory to estimate the critical crack length for fatigue in this prosthesis. It was thus possible to specify the maximum safe size of defect that could be tolerated in use. PMID:8280313

Taylor, D; Martin, C; Cornelis, B; Jones, M E

1993-01-01

396

The new IAEA reference material: IAEA434 technologically enhanced naturally occurring radioactive materials (TENORM) in phosphogypsum  

Microsoft Academic Search

A reliable determination of Technologically Enhanced Naturally Occurring Radioactive Materials in phosphogypsum is necessary to comply with radiation protection and environmental regulations. In this respect, a new phosphogypsum reference material was produced and certified to assist in the validation of analytical methods and the quality assurance of produced analytical results.This paper presents the sample preparation methodology, material homogeneity assessment, characterization

A. Shakhashiro; U. Sansone; H. Wershofen; A. Bollhfer; C. K. Kim; C. S. Kim; G. Kis-Benedek; M. Korun; M. Moune; S. H. Lee; S. Tarjan; M. S. Al-Masri

2011-01-01

397

Hot-pressing of TiC-graphite composite materials  

SciTech Connect

Monolithic TiC and TiC-graphite composites were hot-pressed at temperatures ranging from 1,800 to 2,100 C and with graphite contents up to 30 wt%. Densification behavior was compared for both monolith and composites based on results of microstructural observation and mechanical tests. Monolithic TiC was well densified at the hot-pressing temperature of 1,800 C; significant grain growth and an accompanying decrease in the flexural strength occurred with an increase in hot-pressing temperature. Conversely, the 10 wt% graphite-containing TiC composite required higher temperatures (1,900 to [approximately]2,000 C) to reach a similar degree of densification approaching that of monolithic TiC. As with densification, flexural strength of the composite increased with an increase in hot-pressing temperature. Graphite dispersions in the composites inhibited grain growth of TiC. Contrary to the equiaxed nature of the monolithic TiC grains, in the composite system, the graphite grains were flattened to thin platelets that aligned perpendicular to the hot-pressing axis. Apparent anisotropy in the microstructure was observed in the composites. At a fixed hot-pressing temperature, the relative density of the composites decreased with increasing graphite content.

Ono, T.; Endo, H.; Ueki, M. (Nippon Steep Corp., Kawasaki (Japan). Advanced Materials and Technology Research Lab.)

1993-10-01

398

Nondestructive inspection and evaluation of composite-material flywheels  

SciTech Connect

Several composite panels and flywheel designs were evaluated in support of the Mechanical Energy Storage Technology (MEST) project. Conventional nondestructive evaluation (NDE) technology was used on the panels and flywheels. All flywheels and panels were radiographed and, where practical, were also inspected using ultrasonic techniques. The results provided information about the structural features of flywheels and materials. This information is useful for the quality control of fabrication procedures. The detection of apparent flaws in fabrication cannot be related to the ultimate strength until failure mechanisms in composite materials have been fully defined. Therefore, the location of detected flaws should be recorded for later comparison with dynamic and destructive evaluations.

Boyd, D M; Maxfield, B W; Kulkarni, S V; Schwarber, A J

1982-02-24

399

The histochemical nature of homogeneous amorphous materials in odontogenic epithelial tumors.  

PubMed

The homogeneous acellular materials in the adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor, and calcifying odontogenic cyst were examined histochemically for specific staining of amino acids and protein groups. These materials gave a positive reaction for periodic acid-Sciff (PAS), alloxan-Schiff, and dinitrofluorobenzene-H-acid and low reaction for alcian blue, dimethylaminobenzaldehyde (method for tryptophan) and the Morel-Sisley diazotization method. They appear to have approximately the same composition as enamel matrix and are not amyloid in nature. The materials may be synthesized products from neoplastic epithelium that may originate from enamel organs. PMID:6153217

Mori, M; Makino, M; Imai, K

1980-02-01

400

Multi-objective shape and material optimization of composite structures including damping  

NASA Technical Reports Server (NTRS)

A multi-objective optimal design methodology is developed for light-weight, low cost composite structures of improved dynamic performance. The design objectives include minimization of resonance amplitudes (or maximization of modal damping), weight, and material cost. The design vector includes micromechanics, laminate, and structural shape parameters. Performance constraints are imposed on static displacements, dynamic amplitudes, and natural frequencies. The effects of damping on the dynamics of composite structures are incorporated. Preliminary applications on a cantilever composite beam illustrated that only the proposed multi-objective optimization, as opposed to single objective functions, simultaneously improved all objectives. The significance of composite damping in the design of advanced composite structures was also demonstrated, indicating the design methods based on undamped dynamics may fail to improve the dynamic performance near resonances.

Saravanos, D. A.; Chamis, Christos C.

1990-01-01

401

Silicon carbide composites as fusion power reactor structural materials  

NASA Astrophysics Data System (ADS)

Silicon carbide was first proposed as a low activation fusion reactor material in the mid 1970s. However, serious development of this material did not begin until the early 1990s, driven by the emergence of composite materials that provided enhanced toughness and an implied ability to use these typically brittle materials in engineering application. In the decades that followed, SiC composite system was successfully transformed from a poorly performing curiosity into a radiation stable material of sufficient maturity to be considered for near term nuclear and non-nuclear systems. In this paper the recent progress in the understanding and of basic phenomenon related to the use of SiC and SiC composite in fusion applications will be presented. This work includes both fundamental radiation effects in SiC and engineering issues such as joining and general materials properties. Additionally, this paper will briefly discuss the technological gaps remaining for the practical application of this material system in fusion power devices such as DEMO and beyond.

Snead, L. L.; Nozawa, T.; Ferraris, M.; Katoh, Y.; Shinavski, R.; Sawan, M.

2011-10-01

402

Graphene and carbon nanofiber nanopaper for multifunction composite materials  

NASA Astrophysics Data System (ADS)

The new structures and multifunctional materials is that it can achieve some other special functions while it has ability to carry, such as wave-transparent, absorbing, anti-lightning, anti-heat, anti-nuclear etc. It represents the direction of future development of structural materials. And graphene is the one of two-dimensional atomic crystal free substance only found in the existence and shows great importance for fundamental studies and technological applications due to its unique structure and a wide range of unusual properties. It exhibits great promise for potential applications in chemistry, materials, and many other technological fields. In this paper, we prepare nanopaper through physical vapor deposition (PVD) with a variety in the weight ratio between graphene and nanofiber. Then prepare composite materials with nanopaper and T300/AG80 prepreg by the meaning of autoclave molding. The morphology of nanopaper was characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). And the electrical properties and the EMI shielding performances of these nanocomposites have been investigated experimentally by and four-point probe measurement and vector network analyzer. The experimental results indicate that the composites made from graphene and nanofiber nanopaper have highly electric capability, and the EMI shielding value of composites were all up to -15dB. In the same time the conductivity and the EMI shielding performances were improved with increasing the ratio of graphene in nanopaper. We tested the mechanical properties of composite materials at the same time. The average strength of composite materials is about 2000MPa, the elastic modulus is 130GPa above. We are sure that it can be used as the load-bearing structural material which has a multi-functional performance in the aviation field.

Wu, Chunxia; Lu, Haibao; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2011-03-01

403

Natural Frequencies of Composite Cylindrical Helical Springs Under Compression  

NASA Astrophysics Data System (ADS)

The governing equations of cylindrical isotropic helical springs loaded axially are extended to the study of free vibration of such helices made of composite materials. Stiffness method is used based on the first order shear deformation theory. A helical element has six degrees of freedom at each node, three translations and three rotations. The element stiffness matrix is obtained exactly based on the both complementary functions and the transfer matrix methods.

Kacar, ?lyas; Yildirim, Vebil

404

New composite thermoelectric materials for energy harvesting applications  

NASA Astrophysics Data System (ADS)

The concept of using nanostructured composite materials to enhance the dimensionless thermoelectric figure of merit ZT relative to that for their counterpart homogeneous alloyed bulk crystalline materials of similar chemical composition is presented in general terms. Specific applications are made to the Si-Ge and Bi2--xSbxTe3 systems for use in high-temperature power generation and cooling applications. The scientific advantages of the nanocomposite approach for the simultaneous increase in the power factor and decrease in the thermal conductivity are emphasized insofar as their simultaneous occurrence is enabled by the independent control of these physical properties through the special properties of their nanostructures. Also emphasized are the practical advantages of using such bulk samples both for thermoelectric property measurements and for providing a straightforward path to scaling up the materials synthesis and integration of such nanostructured materials into practical thermoelectric powergeneration and cooling modules and devices.

Dresselhaus, M. S.; Chen, G.; Ren, Z. F.; Dresselhaus, G.; Henry, A.; Fleurial, J.-P.

2009-04-01

405

Bamboo fibre filled natural rubber composites: the effects of filler loading and bonding agent  

Microsoft Academic Search

Bamboo fibre reinforced natural rubber composites were prepared by incorporation of different loadings of bamboo fibre. Two series of composites were studied i.e. composites with and without the presence of a bonding agent. The curing characteristics of the composites were determined and the composites were vulcanized at 150C using a hot press. The properties of the composites such as tensile

Hanafi Ismail; M. R. Edyham; B. Wirjosentono

2002-01-01

406

Statistical prediction of fatigue failure of fibre reinforced composite materials  

NASA Astrophysics Data System (ADS)

A statistical approach is proposed to evaluate the residual strength and life of unidirectional and angle-ply composite laminates subjected to in-plane tensile cyclic stresses. The method is based on the extension of previous static failure criteria describing independently the fibre failure and matrix failure modes, combined with the statistical nature of fatigue failure of fibre-reinforced composites. The static and fatigue strengths of composite laminates at any off-axis angle are evaluated using the fatigue failure functions for the three principal failure modes, which are determined from the fatigue behaviour of unidirectional composites subjected to longitudinal and transverse tension as well as in-plane shear stresses. The evaluations of the fatigue strength of unidirectional E-glass/epoxy laminates under off-axis fatigue loading and angle-ply S-glass/epoxy laminates under in-plane fatigue loading show good agreement between theoretical predictions and experimental results.

Diao, Xiaoxue; Ye, Lin; Mai, Yiu-Wing

1995-05-01

407

Material degradation assessment for stiffened composite shells using metamodelling approach  

Microsoft Academic Search

The intense interest coming from the aerospace industry indicates the need of safe exploitation of composite materials in\\u000a stiffened shell structures. Since stiffened shells are far most consumed structural component, it is important to study the\\u000a behaviour of material degradation to evaluate the safe design guidelines. Moreover, current numerical procedures cannot simulate\\u000a the collapse of stiffened shells with sufficient reliability

Kaspars Kalnins; Rolands Rikards; Janis Auzins

408

Application of magnetic abrasive polishing to composite materials  

Microsoft Academic Search

Magnetic abrasive polishing (MAP) is an advanced machining process that can produce smoother surfaces in many material types.\\u000a The present study conducted an experimental assessment of MAP for a newly developed, non-ferrous and aluminum-based composite\\u000a material. A permanent magnet was installed under the workpiece to enhance its magnetic flux density, which had proved insufficient\\u000a for effective MAP. The success of

Tae-Wan Kim; Dae-Min Kang; Jae-Seob Kwak

2010-01-01

409

Inhibition of catalytic oxidation of carbon\\/carbon composite materials  

Microsoft Academic Search

An investigation coupling experimental efforts with computational chemistry analysis was conducted to study the inhibition effects of phosphorous or boron on the oxidation of carbon\\/carbon composite materials catalyzed by potassium or calcium acetate (KAC or CaAC). Commercial aircraft brakes were used, which are exposed during use to K- or Ca-containing runway deicing agents. The reactivity of inhibitor-doped carbon materials was

Xianxian Wu

2002-01-01

410

Simulation of ultrasonic array imaging of composite materials with defects.  

PubMed

Ultrasonic transducer arrays are extensively used for the nondestructive evaluation of materials for aerospace and other applications. However, their use with composites requires some technique development because of reflections at the layer boundaries and the effects of attenuation. When used in full matrix capture mode, algorithms such as the total focusing method (TFM) must be applied to obtain the image. In composite materials, improvement to the algorithm is required to include the effects of material anisotropy (affecting wave speed) and optimum aperture limits to optimize the signal-to-noise ratio and location detection for a defect in the material. This paper presents simulations of the ultrasonic array signals in multilayer anisotropic materials with and without a simulated defect. A kernel model for plane wave propagation in the material is combined with an angular spectrum decomposition (for finite transducer elements) and transducer frequency response, to model the full array signals. Inclusion of the defect is through its far-field scattering response. The model facilitates the study of imaging algorithm development by identification of the effects of anisotropy, signal-to-noise ratio, and aperture limit. An analytical method for the calculation of the effective group velocity in the composite at low frequency is demonstrated, permitting rapid calculation of time delay laws in practice. PMID:24658724

Humeida, Yousif; Pinfield, Valerie J; Challis, Richard E; Wilcox, Paul D; Li, Chuan

2013-09-01

411

Alternative processing methods for tungsten-base composite materials  

SciTech Connect

Tungsten composite materials contain large amounts of tungsten distributed in a continuous matrix phase. Current commercial materials include the tungsten-nickel-iron with cobalt replacing some or all of the iron, and also tungsten-copper materials. Typically, these are fabricated by liquid-phase sintering of blended powders. Liquid-phase sintering offers the advantages of low processing costs, established technology, and generally attractive mechanical properties. However, liquid-phase sintering is restricted to a very limited number of matrix alloying elements and a limited range of tungsten and alloying compositions. In the past few years, there has been interest in a wider range of matrix materials that offer the potential for superior composite properties. These must be processed by solid-state processes and at sufficiently low temperatures to avoid undesired reactions between the tungsten and the matrix phase. These processes, in order of decreasing process temperature requirements, include hot-isostatic pressing (HIPing), hot extrusion, and dynamic compaction. The HIPing and hot extrusion processes have also been used to improve mechanical properties of conventional liquid-phase-sintered materials. Results of laboratory-scale investigations of solid-state consolidation of a variety of matrix materials, including titanium, hafnium, nickel aluminide, and steels are reviewed. The potential advantages and disadvantages of each of the possible alternative consolidation processes are identified. Postconsolidation processing to control microstructure and macrostructure is discussed, including novel methods of controlling microstructure alignment.

Ohriner, E.K.; Sikka, V.K.

1995-12-31

412

Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials  

NASA Technical Reports Server (NTRS)

Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

Jordan, William

1998-01-01

413

Novel Microstructures for Polymer-Liquid Crystal Composite Materials  

NASA Technical Reports Server (NTRS)

There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.

Magda, Jules J.

2004-01-01

414

Biomimetic-inspired joining of composite with metal structures: A survey of natural joints and application to single lap joints  

NASA Astrophysics Data System (ADS)

Joining composites with metal parts leads, inevitably, to high stress concentrations because of the material property mismatch. Since joining composite to metal is required in many high performance structures, there is a need to develop a new multifunctional approach to meet this challenge. This paper uses the biomimetics approach to help develop solutions to this problem. Nature has found many ingenious ways of joining dissimilar materials and making robust attachments, alleviating potential stress concentrations. A literature survey of natural joint systems has been carried out, identifying and analysing different natural joint methods from a mechanical perspective. A taxonomy table was developed based on the different methods/functions that nature successfully uses to attach dissimilar tissues (materials). This table is used to understand common themes or approaches used in nature for different joint configurations and functionalities. One of the key characteristics that nature uses to joint dissimilar materials is a transitional zone of stiffness in the insertion site. Several biomimetic-inspired metal-to-composite (steel-to-CFRP), adhesively bonded, Single Lap Joints (SLJs) were numerically investigated using a finite element analysis. The proposed solutions offer a transitional zone of stiffness of one joint part to reduce the material stiffness mismatch at the joint. An optimisation procedure was used to identify the variation in material stiffness which minimises potential failure of the joint. It was found that the proposed biomimetic SLJs reduce the asymmetry of the stress distribution along the adhesive area.

Avgoulas, Evangelos Ioannis; Sutcliffe, Michael P. F.

2014-03-01

415

Thermo-viscoelastic analysis of composite materials, volume 1  

NASA Technical Reports Server (NTRS)

Advanced composite materials, especially graphite/epoxy, are being applied to aircraft structures in order to improve performance and save weight. An important consideration in composite design is the residual strength of a structure containing holes, delaminations, or interlaminar damage when subjected to compressive loads. Recent studies have revealed the importance of viscoelastic effects in polymer-based composites. The viscoelastic effect is particularly significant at elevated temperature/moisture conditions since the matrix material is strongly affected by the environment. The solution of viscoelastic problems in composites was limited to special cases which can be solved by classical lamination theory. A finite element procedure is presented for calculating time-dependent stresses and strains in composite structures with general configurations and complicated boundary conditions. Using this procedure the in-plane and interlaminar stress distributions and histories in notched and unnotched composites were obtained for mechanical and thermal loads. Both two-dimensional and three-dimensional viscoelastic problems are analyzed. The effects of layup orientation and load spectrum on creep response and stress relaxation were also studied.

Lin, K. Y.; Hwang, I. H.

1988-01-01

416

Structure of boundaries in composite materials obtained using explosive loading  

NASA Astrophysics Data System (ADS)

We have presented the results of studying the fine structure of interphase boundaries for a number of composite materials obtained by methods of explosive welding and explosive compacting of powder mixtures. Joints of different metals (titanium-low-carbon steel, copper-tantalum) and metals with refractory carbides (chromium carbide-titanium) have been investigated. Under welding, pairs differed from each other by the type of interaction. It has been found that, in these composites, interphase boundaries exhibit a final thickness on the order of 200 nm, throughout which the composition of the material changes gradually from a composition that corresponds to one of the components of the composite to a composition that corresponds to the second component. It has been shown that the structure of interphase boundaries is complex. With the limited solubility of components along boundaries, two fairly thick crystalline interlayers are detected, the total thickness of which is equal to the total thickness of the boundary; between the interlayers, there is a thin (to 5-7 nm in thickness) interlayer with a crystalline or amorphous structure.

Lysak, V. I.; Kuz'min, S. V.; Krokhalev, A. V.; Grinberg, B. A.

2013-11-01

417

The steam reforming of phenol over natural calcite materials  

Microsoft Academic Search

Five natural calcite materials of different geographical origin were studied towards the steam reforming of phenol reaction and the activity results obtained were correlated with some of their physico-chemical properties. It was found that the specific catalytic activity (?mol\\/(m2s)) of the calcite material following calcination at 850C was not correlated with the BET area and the primary crystal size of

Domna A. Constantinou; Angelos M. Efstathiou

2009-01-01

418

Hazardous materials and natural disaster emergencies: Incident action guidebook  

Microsoft Academic Search

This guidebook\\/workbook\\/directory will help to prepare for and act effectively during a hazardous material or natural disaster emergency. It is a compilation of procedural steps, checklists, forms, directories, diagrams, organization charts, and other materials that are helpful for planning, training and response action. Most important, the guidebook provides a plan of action in concise, step-by-step form. Topics considered include: evacuation

Terrien

1984-01-01

419

Determination of natural actinides and plutonium in marine particulate material  

Microsoft Academic Search

The natural actinides ²²⁷Ac, ²²⁸Th, ²³°Th, ²³²Th, ²³⁴Th, ²³¹Pa, ²³⁸U, and ²³⁴U and the ..cap alpha..-emitting plutonium isotopes are determined in samples of suspended marine particulate material and sediments. Analysis involves total dissolution of the samples to allow equilibration of the natural isotopes with added isotope yield monitors followed by coprecipitation of hydrolyzable metals at pH 7 with natural Fe

Robert F. Anderson; Alan P. Fleer

1982-01-01

420

Fractography of modern engineering materials: Composites and metals, Second volume  

SciTech Connect

This book contains the manuscripts of eleven papers that were presented at the Second Symposium on Fractography of Modern Engineering Materials held in May 1992. The numerous advances in materials science in the six year period following the First Symposium dictated this second meeting. Not only had new materials been developed in the intervening years, but understanding of older materials had also progressed. Similarly, advances in the technology and the techniques of fractography had occurred. The objective of the symposium was to extend the colloquy on fractography to include these many advances. The paper may be divided into three sections: Unique Fractographic Techniques; Metallic Materials; Polymeric and Composite Materials. The section titles reflect the diversity of materials discussed in the meeting. The range of materials included cross-linked polyethylene, AISI 52100 steel, 2024 aluminum, and a variety of organic and metal matrix fibrous composites. The case studies presented also covered a wide range. They included failure investigations of an antenna used in deep space exploration and chemical storage tanks. Advances in the techniques of fractography were also reflected in a number of presentations; quantitative techniques and expert systems were also subjects of presentations. A short precis of each paper is included here to assist the readers in identifying works of particular interest.

Masters, J.E.; Gilbertson, L.N. (eds.)

1993-01-01

421

Nanostructured polymer-metal composite for thermal interface material applications  

Microsoft Academic Search

Continued miniaturization in combination with increased performance of microelectronics has generated an urgent need for improved thermal management techniques in order to maintain reliability of systems and devices. Development of advanced thermal interface materials has been identified as crucial, absorbing a portion of the advancements necessary within packaging technology. In this paper we introduce a novel nanostructured polymer-metal composite for

Bjrn Carlberg; Teng Wang; Yifeng Fu; Johan Liu; Dongkai Shangguan

2008-01-01

422

Graphics and composite material computer program enhancements for SPAR  

NASA Technical Reports Server (NTRS)

User documentation is provided for additional computer programs developed for use in conjunction with SPAR. These programs plot digital data, simplify input for composite material section properties, and compute lamina stresses and strains. Sample problems are presented including execution procedures, program input, and graphical output.

Farley, G. L.; Baker, D. J.

1980-01-01

423

New materials for electrochemical sensing I. Rigid conducting composites  

Microsoft Academic Search

The development of composites based on conductive phases dispersed in polymeric matrices has led to important advances in analytical electrochemistry, particularly insensor devices. These new materials combine the electrical properties of graphite with the ease of processing of plastics (epoxy, methacrylate, Teflon, etc.) and show attractive electrochemical, physical, mechanical and economical features compared to the classic conductors (gold, platinum, graphite,

F. Cspedes; E. Martinez-Fbregas; S. Alegret

1996-01-01

424

Manufacture of composite electrochemical materials from suspended electrolytes  

NASA Astrophysics Data System (ADS)

New composite electrochemical materials on a metallic substrate synthesized from suspended electrolytes with additives of kaolin and bentonite powders of the nanosized fraction are studied. The limiting concentrations of the additives in the electrolyte that warrant the retention of the decorative and special properties of the microchromium coating are determined.

Plotnikova, O. G.; Mal'kova, M. Yu.; Gruzd, N. S.; Zadiranov, A. N.; Paretskii, V. M.

2013-12-01

425

Thermal Expansion Coefficients of Composite Materials Based on Energy Principles  

Microsoft Academic Search

Bounds on effective thermal expansion coefficients of isotropic and anisotropic composite materials consisting of isotropic phases are derived by employing extremum principles of thermoelasticity. Inequalities between certain approximate and exact forms of the potential and complementary energy functionals are first estab lished. These inequalities are then used in conjunction with a new method for minimizing the difference between upper and

R. A. Schapery

1968-01-01

426

Ultrasonic inspection of impact induced damage in polymeric composite materials  

NASA Astrophysics Data System (ADS)

An account is given of current performance capabilities in the ultrasonic inspection of graphite-epoxy composite materials of both simple laminate and sandwich type. Attention is given to damage types ranging from barely-visible impact effects to complete destruction. These ultrasonic inspection procedures have been implemented in the case of certification tests for the EH 101 helicopter.

Pezzoni, R.; Merletti, L.; Battagin, G.; Denis, R.

1992-09-01

427

Development of a pultruded composite material highway guardrail  

Microsoft Academic Search

Fiber-reinforced polymer (FRP) composite materials are being used to develop products for use as highway appurtenances, such as, sign supports, luminaire supports and guardrails (crash barriers). These structures, that are located alongside highways and roads, are subjected to vehicular impacts and must be designed to be crashworthy to ensure the safety of the driving public. This paper reviews an ongoing

L. C Bank; T. R Gentry

2001-01-01

428

On some applications of gradient elasticity to composite materials  

Microsoft Academic Search

Some applications of the gradient theory of elasticity to composite materials are discussed. A brief introduction to gradient theory is given and some mathematical aspects are provided. Of particular importance is a constitutive equation of a higher-order strain gradient theory, and a particular form of gradient theory for which the RuAifantis theorem holds. Applications include a fiber pullout from a

L. Teneketzis Tenek; E. C. Aifantis

2001-01-01

429

Methods of selecting raw material composition for asphalt production  

Microsoft Academic Search

It is recommended that raw material for oxidation should be prepared by mixing two components with certain boiling ranges and chemical-group compositions. The heavy component may be a residue obtained by high-vacuum distillation of a long residuum, or it may be an asphalt produced in the propane deasphalting of a reduced crude. The light component may be a long residuum,

R. S. Akhmetova; E. P. Glozman

1974-01-01

430

Neural computing of effective properties of random composite materials  

Microsoft Academic Search

The effective response of disordered heterogeneous materials, in general, is not amenable to the exact analysis because the phase geometry may not be completely specified. The present paper deals with the problem of effective properties such as thermal conductivity, electrical conductivity, dielectric constant, magnetic permeability, and diffusivity in the realm of disordered composites. Even though all these properties are analogous,

Victor A. Gotlib; Tadanobu Sato; Abraham I. Beltzer

2001-01-01

431

Making Composite-Material Parts At Moderate To High Rates  

NASA Technical Reports Server (NTRS)

Composite-material (matrix/fiber) structural components manufactured at moderate to high rates in production-line-style processes, according to proposal. In method, production lines largely automated and takes advantage of fact matrix resins cured by electron beams in addition to heat. Net result reductions in production times and costs.

Farley, Gary L.

1995-01-01

432

Energy Harvesting Devices Using Macro-fiber Composite Materials  

Microsoft Academic Search

This study addresses the experimental validation of a design methodology for an energy harvesting device utilizing macro-fiber composite (MFC) materials. The energy harvesting device is composed of a cantilever beam with MFC elements, a tip mass, a rectifier, and an electrical resistance. A theoretical model of the energy harvesting device was developed for the estimation of generated power, voltage, and

Hyun Jeong Song; Young-Tai Choi; Norman M. Wereley; Ashish S. Purekar

2010-01-01

433

Impact damage detection of composite materials by fiber Bragg gratings  

Microsoft Academic Search

Usage of fiber-optic Bragg gratings (FBG) for strain measurement is well-known technique in structural health monitoring (SHM). However, this technique based on shift of spectral peak, suffers from different spurious signals, particularly caused by thermal effect. We present here a method for impact damage detection of composite materials based on FBG without thermal disturbance. This method is based on the

Zoran Djinovic; Michael Scheerer; Milos Tomic

2011-01-01

434

State of composite material structure control in situ  

NASA Astrophysics Data System (ADS)

A review is given of methods available for the metallurgical control and NDT evaluations of composite materials with attention given to their limitations. Among the techniques examined are holography, acoustic emission, and extensometry. The development of automated ultrasonic control techniques is leading to more routine use in such industrial applications as aircraft fabrication.

Huther, M.; Jouan, M.

435

The measurement of porosity in composite materials using infrared thermography  

Microsoft Academic Search

The possibility of using infrared tomography for inspecting fiber-reinforced polymer matrix composite materials for the presence and extent of porosity is investigated experimentally. The technique involves heating one face of the sample with a laser and observing the temperature rise on the other face as the heat diffuses through the sample. Experimental results obtained for carbon\\/epoxy samples with a range

M. P. Connolly

1992-01-01

436

Fracture Mechanics for Delamination Problems in Composite Materials  

Microsoft Academic Search

A fracture mechanics approach to the well-known delamination problem in com posite materials is presented. Based on the theory of anisotropic laminate elasticity and interlaminar fracture mechanics concepts, the composite delamination problem is for mulated and solved. The exact order of the delamination crack-tip stress singularity is determined. Asymptotic stress and displacement fields for an interlaminar crack are obtained. Fracture

S. S. Wang

1983-01-01

437

Reaction behavior during heating biomass materials and iron oxide composites  

Microsoft Academic Search

Effective utilization of biomass materials as a reducing agent in the ironmaking process is one of the key technologies for environmental protection. In this work, in order to study the possibility of effective use of woody biomass as a reducing agent in the carbon composite method, we carried out experiments of the thermal decomposition of woody powder and reduction of

Yasuaki Ueki; Ryo Yoshiie; Ichiro Naruse; Ko-ichiro Ohno; Takayuki Maeda; Koki Nishioka; Masakata Shimizu

438

The optimization of a gypsum-based composite material  

Microsoft Academic Search

Contemporary requirements for gypsum-based composite materials (GBCM) for rendering or plastering include controlled setting time, good workability, sag resistance, high compressive and flexural strength, perfect bond to concrete or brick, water resistance, and improved heat and noise insulation. The application of a number of chemical admixtures and mineral additives was found to be necessary to provide the required performance for

M Arikan; K Sobolev

2002-01-01

439

Nonlinear Optical Waveguides Using Carbon Nanotube-Polyimide Composite Material  

Microsoft Academic Search

We fabricated buried waveguide structures with a carbon nanotube-polyimide composite material as cores and examined their actual operation of saturable absorpton with various short pulse light sources from 0.3ps, 20MHz to 2.5ps, 1GHz.

Youichi Sakakibara; Taro Itatani; Shun Matsuzaki; Toshiyuki Oomuro; Emiko Itoga; Madoka Tokumoto; Masafumi Yamashita; Hiromichi Kataura

2006-01-01

440

Hysteresis heating based induction bonding of composite materials  

Microsoft Academic Search

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni\\/PSU). An excellent

Witchuda Suwanwatana

2004-01-01

441

Filament Composite Material Landing Gear Program, Volume II.  

National Technical Information Service (NTIS)

The design, fabrication and test of a boron composite material landing gear assembly interchangeable in both geometry and performance with the main landing gear of the A-37B aircraft is reported. One full size landing gear assembly was tested. This assemb...

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